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This all in one car seat transforms from a rear-facing infant seat to a forward-facing child seat, to an older-child booster.

This eliminates the need to purchase new car seats as your child grows (source).

If a Swiss Army Knife were a car seat, it would be the Diono Rainier All-In-One Convertible Car Seat. In addition to having the ability to transition between seats, the Diono Rainier also has a unique SuperLATCH system.

This system makes installation quick and easy, getting you on your way in a snap. Top things off with great adjustability and NCAP crash testing status, and you have a child seat that will last without breaking the bank.

Top Features

Collision Protection

Starting with the reinforced steel frame, the Diono Rainier is built for safety.  Add aluminum reinforced sides for an extra-sturdy core that protects your child in the event of a collision. The sidewalls of the Diono Rainier are reinforced and extra-deep. 

These sidewalls are then topped with energy-absorbing EPS foam. The combination of these features gives your child superior head and body protection.

Convertible Seat

As the name suggests, the Diono Rainier is a completely hybrid car seat.  This one seat transitions from rear-facing infant seat, to a forward-facing child seat, to big-kid booster seat.

Rear-facing Infant Seat

As a rear-facing infant seat, it comfortably accommodates children from 5 to 50 pounds.  It is recommended that your child ride rear-facing for as long as possible. A typical rear-facing infant seat has a maximum weight limit of 30-35 pounds. With a 50-pound maximum weight limit, this seat keeps your child rear-facing for longer, which is the safest option.

Forward-Facing Child Seat

As a forward-facing child seat, this seat has a weight range of 20-90 pounds and a height maximum of up to 57 inches.  This gives the Diono Rainier one of the highest forward-facing capacities of any car seat in a 5-point harness on the market.  

Typically, a child doesn’t reach 90 pounds until they are around 9 years old. Extra-long leg supports allow older children to be comfortable in the seat for as long as possible.

Big-kid Booster

The last seat that can be transitioned to is a big-kid booster seat.  Booster mode is suitable for children between 50 and 120 pounds and up to 57 inches in height.

This feature is a high back booster to surround your older child the most safety and support as possibleFor this mode, the harness is removed and the vehicle’s seatbelt is used to restrain and protect your child.


Because of its convertible nature, this car seat offers many different ways to adjust. The lower buckle has three different positions to accurately fit your child: 4”, 6”, and 8”.The headrest of the Diono Rainier has 12 adjustable positions for comfort and safety.

There are also five options for shoulder positioning that can be adjusted for the perfect fit.  All of the adjustability options allow the seat to comfortably and safely fit your child as he grows. 

Ease of Installation

As previously mentioned, this car seat is equipped with a unique installation system that allows for easy, worry-free installation every single time.  This is the SuperLATCH system. The SuperLATCH system is unlike any other. Only Diono car seats are equipped with SuperLATCH.  

Like most other modern car seat models, this system utilizes the vehicle’s existing LATCH anchors.  Most car seats have a single metal clip that attaches to the anchors on the LATCH system.

The SuperLATCH system has four metal clips that attach to your vehicle’s LATCH anchors, making the connection stronger between the seat and the car. This system keeps your car seat secure to your vehicle in virtually any type of collision.

What we Liked

Busy parents on-the-go look for products that are easy to use and convenient in many ways.  The Diono Rainier offers multiple convenient qualities that busy parents appreciate.  

Compact Folding

Traveling with kids, let alone a car seat, is never an easy feat. If you are a family who likes to travel, the Diono Rainier should be a seat to consider.  While the seat itself is bulky, it folds completely flat for travel and storage. It is also FAA certified, so it is cleared for use on an airplane.


Another convenient feature of this car seat is its positioning in the car itself. As our children get older and older, they also get heavier and heavier.  While the child seat itself may be large and somewhat bulky, it sits low on the vehicle car seat.  

This quality makes it easier for parents to lift their children up into the child seat. It’s hard enough to wrestle with your child to get them safely buckled in their seat. Making it easier to lift them into the seat helps to ease the struggle. 

Cup Holder

As our children grow, they have different needs.  They also tend to get more and more unhappy in the car.  Keeping children distracted with drinks and snacks in the car seat helps make the longer rides more enjoyable for everyone.  

Your purchase of the Diono Rainier includes a cup holder that attaches to the car seat, keeping snacks or drinks in reach for your child. This feature can hopefully help keep your child distracted long enough for an enjoyable ride.

Washable Cover 

The last convenience feature of the Diono Rainier is the washable seat cover.  Remember those snacks and drinks we just mentioned? They’re helpful to have close by, but tend to get crumbs and spills all over the car seat.  

This seat has an easily removable seat cover that is both machine washable and dryable. I don’t know about you, but not having to wash something by hand is a huge win in my book.  Simply remove and wash whenever the cover is dirty. This will keep your car seat looking fresh and will help it last for years to come.

Expiration Information

The Diono Rainier has a 12-year product life from the date of purchase.  This is an industry-leading time-span for the life of a car seat.

Warranty Information

As with many other car seat companies, Diono offers a one-year limited product warranty.  This warranty covers any defects to the parts that make up the car seat. This warranty is only valid when proof of purchase can be verified, so make sure to keep your receipt for at least a year.

How to use a Diono Rainier as a Booster

To use a Diono Rainier as a Booster, you will first need to convert the seat to booster mode. The first thing you will need to do is remove the harness from the car seat.

This will require you to remove some screws with a Phillips head screwdriver. Next, the car seat needs to be attached to your vehicle’s LATCH anchors using the SuperLATCH system. Lastly, the seatbelt of your vehicle needs to be routed through the shoulder belt clip behind the side wings of the headrest. Now, your Diono Rainier is ready to be used as a booster seat.

Other Model Comparisons

Diono Rainier is the base model and has been expanded upon since its creation. Here is how it compares to the other models

Diono Rainier 2aX

The Diono Rainier 2aX is a convertible car seat with many similar safety and design features to the Diono Rainier. Both car seats feature Diono’s proprietary SuperLATCH system, ample amounts of head and side-impact protection, and adjustable straps and buckles. The 2aX offers rear-facing protection from 5-50 pounds, and forward-facing protection up to 65 pounds. 

However, 65 pounds is the maximum weight for this car seat. The Diono Rainier 2aX does not convert into a booster seat. Another notable difference is that the headrest of the 2aX does not have the 12 adjustable positions that the Diono Rainier offers.

Diono Rainier 2aXT

The Diono Rainier 2aXT is extremely similar to the original Diono Rainier.  These seats are almost identical except for some small differences. First, the original Rainier seat weighs 28.4 pounds while the 2aXT 31.3 pounds.  Now, while the 2aXT is heavier, it has smaller dimensions, so it takes up less space in the back of your car.

The 2aXT also does not come with a cup holder included, so that maybe something you need to consider depending on your preferences. Lastly, the 2aXT has a more advanced “nesting feature” than the original Rainier.  This is referring to the insert that keeps your infant more secure in a large car seat. 

The nesting insert in the 2aXT is meant to keep your newborn safe from 5 pounds and up. Other than these differences, the 2aXT and the original Rainier car seat have the same weight requirements and features.

Diono Radian

The Radian is Diono’s other premiere convertible car seat line. For direct comparison purposes, we will be comparing the Rainier with the Radian rXT convertible car seat. The Radian rXT has shares several important features with the Rainier.


First, it can be used as a rear-facing infant seat, forward-facing child seat, and big kid booster.  Transitioning between modes in the Radian is very similar to what is required in the Rainier as well. Both seats feature steel frames and EPS foam for impact protection.  They also both share the adjustability of a 12-position headrest, 5 shoulder, and 3 buckle positions.  


To find differences between these seats, you have to look a little closer. First, the rear-facing weight limit in the Radian is five pounds less than that of the Rainier.  The Radian accommodates children from 5-45 pounds rear-facing while the Rainier goes up to 50 pounds in its rear-facing mode.

Second, and perhaps the shining quality of the Radian, is the fact that three of these seats can fit side-by-side in most mid-size vehicles. Fitting multiple car seats in your vehicle is not always a possibility.  With the Radian, it is possible to accommodate three children in your backseat safely and comfortably. 

This makes the Radian perfect for large families with young children close in age. Other than that, the only other main difference is the expiration date.  While the Rainier does not expire for 12 years from the date of purchase, the Radian has a 10-year life from the date of purchase. 

Diono Recall (2017)

In 2017, Diono issued a recall for some of their car seats, the Rainier being one of them. If your Rainier car seat was made between 2013 and 2017, it falls into this recall category.

When installed in your vehicle with the seatbelt only, the car seat was not performing properly in a crash. To remedy the situation, Diono sent out new chest clips and energy-absorbing pads with instructions on how to replace them.  If your Rainier car seat fits into this category, contact Diono for your recall products and instructions.


If the Rainier is the car seat you choose, there is also the option of purchasing summer cover for your car seat. It can’t be hard to imagine that sitting in a car seat on a hot day is more than uncomfortable.

The optional summer cover for the Rainier car seat can help keep your child cool during the hot summer months.

This particular cover is made of plush, cotton fabric, similar to a towel.  It is soft against your child’s skin, while also promoting good airflow.  It is also absorbent and breathable to keep moisture away from your baby’s skin. On top of keeping your baby cool and dry, this cover also protects the fabric of your car seat so that it lasts for longer.


Overall, the Diono Rainier is a strong and sturdy car seat with a lot of safety features to put your mind at ease. While it is bulky and heavy, it is relatively easy to install.  Because of its size and weight, it would be best to use this car seat if you plan to leave it in one car and not move it around a lot.

It can also be tricky to transition between rear-facing, forward-facing, and booster modes.  However, if you do not need to go back and forth between modes, then this is not a big problem. The Diono Rainier would be best for a family who is interested in one seat for their child from birth and on.