Diono Connect3 RXT Backless Booster Review: Under 17 Inches, Sold in Twos

Under 17 inches, and why the number is published that way

Diono says less than 17 inches wide, not 16.8 or 16.4. That is the shape of a number a manufacturer can stand behind across a production run, and it is enough to do arithmetic with: three seats at under 17 inches is under 51 inches of row. A 15.16 inch booster is narrower still, and a 17 inch convertible sits right at the edge.

Width alone does not make a three-across work. What usually fails is the buckle. The center seat’s buckle stalk ends up under the outboard booster’s armrest, and a child cannot get a hand in to latch it. Diono’s answer is a seat pan contoured around the EasyPath lap belt guides, which leaves a channel at the inboard edge for fingers to reach the buckle.

That contour is worth understanding before you buy, because it is the one feature here that a photo will not explain. Run your hand along the inboard side of the seat pan. The cutout near the guide is where the buckle access comes from, and it is the reason this seat is easier to live with in a tight row than a flat slab of foam.

Two in the box, and what that assumes

This is a pack of two, in Pink Cotton Candy. That is a fine arrangement for twins, for two children close in age, or for a second row where you want matching seats on both sides of a center seat. It is a poor arrangement for one child in one car, because you will store the second seat in a garage for four years and then forget you own it.

The second seat is not useless, though. A spare that lives in a trunk or a grandparent’s car is the difference between a carpool text you can say yes to and one you cannot. If you already know you need two seats in two vehicles, buying the pair is the straightforward version of that plan.

Check the three-across guide before you commit to the pair for a specific row. The 2-pack tells you the seats are narrow. It does not tell you your bench, your buckle stalks, or your door openings are going to cooperate.

40 to 120 lb, and the height number Diono does not print

The weight range is 40 to 120 lb, which is one of the wider windows in this class. The listing gives no height range at all, and no age. That is a real gap, because a backless booster’s job is belt geometry, and belt geometry is a height question: the lap belt has to land on the hip bones and the shoulder belt has to cross the collarbone on a child sitting flat against the vehicle seat back.

So you test it in the car. Sit the child on the booster, route the belt, and look at where the diagonal crosses. If it is on the neck, the seat is not doing its job for that child yet regardless of what the scale says. If the lap belt rides up onto the belly, the same. The 120 lb ceiling covers a lot of years, but it is a maximum, not a prescription.

There is a shoulder belt positioning clip included for exactly this, and it belongs on the diagonal section at shoulder height. Diono describes it as being for the best install with kids of any size, which is the company admitting the clip is doing the fitting work.

LATCH straps, front accessible

The connectors are described as premium LATCH with easy-release straps reachable at the front of the booster. On a backless seat that matters more than it does on a convertible, because the seat sits low and the anchor bars are behind it. Straps you can pull from the front mean you are not lying across the back seat to unhook a seat you are about to move.

There is a built-in carry handle, and the pair is light enough that the handle is genuinely the way you move it. This is a seat that goes from the car to the garage shelf and back without a fight.

As with every booster, the anchors hold the seat, not the child. The vehicle belt holds the child. And your vehicle sets the limit for what those lower anchors can take, so read the owner’s manual for the seating position you plan to use. A backless booster does not use a top tether, and this one does not list one.

The cup holders are part of the width math

Two removable cup holders are included, and Diono is specific about where they go in a three-across: they nest between Connect3 seats, and they stow under the booster when not in use or when you are on the go. That is a rare case of a manufacturer thinking about the failure mode instead of the feature list.

Cup holders are also the first thing that breaks a three-across. A holder that sticks out six inches on the outboard side of a seat is six inches you did not budget, and it is usually pressed against a door panel or a second seat. Nesting them between seats converts a protrusion into a shared accessory.

The seat base is Diono’s 2TexFoam. The listing does not detail the layers or thickness, so the honest description is a foam seat base with a fabric cover, and the cover comes off.

Where this seat stops

No back and no headrest. In a vehicle with a low seat back or no adjustable head restraint in that position, a sleeping child’s head has nothing to lean against, and the shoulder belt has nothing to keep it in place above the shoulder. The high-back version of the same shell adds an 11-position headrest that adjusts for height and a backrest that reclines in two positions, and it converts to backless later.

That conversion is the argument for the high-back if you are buying for one child: you get the narrow shell, you get the head support now, and you get the backless mode at 120 lb or whenever the child outgrows the headrest. The pair is the right buy when the row is the problem and the head support is already handled by the vehicle.

Either way, measure before you buy. The width chart is the place to check what your current seats already take up, because a 17 inch booster next to two 19 inch convertibles is still not a three-across, no matter how the booster is shaped.