NOT RECOMMENDED : There is very little need for a convertible booster seat, such as the safety 1st Prime AP car seat. Extended harnessing is a safer option for children; keeping them in a 6 point harnes until 7 years of age.
Additionally the Safety 1st prime is a manually adjusted seat meaning you need to un-install the car seat whenever you want to change the harness height; in comparison the britax maxi rider is a better option with a easy adjust harness.
Custodian Replacement
The Safety 1st Prime AP car seat is designed to replace the Safety 1st Custodian Plus II. A seat which found it own little niche where there were contoured seats or a small gap where a harnessed seat was required to squeeze in. Unfortunately the Safety 1st Prime A is marginally wider meaning it is better options to fit into a narrow gap (infa quattro or britax slim line).
Wide head rest
Additionally the head rest is somewhat wider than the Custodian Plus II meaning it causes 2 problems then first problem is when the car seat is placed in the middle position, it will obscure the rear vision view through the back, making it harder for some to drive, secondly the wider head rest also causes problem when placed on the side of the car either passenger or drivers side with the head rest hitting the side pillar when te head rest is raise more than 1.5 cm (out of a maximum of 6cm) in booster mode.
Seat-belt installation
The path of the harness at the back of the seat is an issue when the tether is tightened, causing it be be difficult to tighten the harness around your child. When the tether is loosened off to release some of the pressure, the tether may appear rather loose. This same issue will happen when the foam of the car seat is spongy and with a long buckle stalk.
Thankfully Safety first have corrected the seat belt path; so that it no longer locks the armrest when used in vehicle with ALR (automatic locking retraction). However you will still need to use a lockie ;as it does not not have a tight path; like the Maxi Cosi Aura.
Prime AP car seat Manual Harness
With so many restraints out there with a hassle free harness; it is surprsing that Safety 1st has gone for a manual rethread of the harness . This is a significant dis-advantage when selecting a car seat for your toddler.
Summary Safety 1st Prime AP car seat and Booster
Not Recommended – There are better seats out there for the money; the seat is designed primarily for people with large SUV’s where head room is not an issue. The manual re-thread means that it is not suitable for grand parents; or parents who are not comfortable re-installing the car seat on their own. Lastly the installation is extremely difficult and it is recommended to ues a Profession baby car seat fitter.