Request a catalogue

Available Catalogues

I'm interested in:
  • Motorsport
  • Motorcycle
  • Performance
  • Tools and Workshop

Car Seat Buying Guide

No matter what age your little cherub is, looking for a car seat for them can feel like an impossible task. There are multiple regulations to consider as well as the law, not to mention all the jargon that seems to make no sense…. well, that's where this buying guide comes in. This handy guide will talk you through all the regulations and the law in an easy-to-understand way and we've even included a jargon buster at the end. You can also call our team at Demon Tweeks, they are all fully trained and will offer the best advice for you and your family.


Firstly, let's cover the UK law on car seats. The law states that you must normally use a car seat until your little one reaches 12 years old or 135cm tall, whichever comes first. Children over 12 years old or 135cm tall must wear a seat belt. There are some very specific reasons when you don't need to use a car seat – but your child is ALWAYS much safer in a child car seat in the event of an accident.


Next, lets cover the regulations. At the time of writing (March 2022) there are 2 regulations in force in the UK covering child car seats – these are R44/04 and R129 which is sometimes referred to as i-Size. The R44/04 regulation seats are being phased out in the next couple of years and while you won't be able to buy them, they are still completely legal to use.

Group Also known as Weight range Approx age range
Group 0+ Infant carrier or baby seat up to 13kg birth to 12-15 months
Group 0/1 up to 18kg birth to 4 years
Group 0+/1/2 Combination seat up to 25kg birth to 6 years
Group 0+/1/2/3 Combination seat up to 36kg birth to 12 years
Group 1 9 to 18kg 9 months to 4 years
Group 1/2/3 9 to 36kg 9 months to 12 years
Group 2/3 15 to 36kg 4 to 12 years
Group 3 Booster cushion 22 to 36kg 6 to 12 years


These seats are collated by 'Groups' and are based on the weight of your child – please note the ages are approximate. R44/04 seas only require you to keep your little on rear-facing until they reach 9kg but we always recommend keeping them rear-facing as long as you can as it's a much safer way for babies to travel.


Sometimes called i-Size (which isn't technically correct, while most seats that are R129 certified are also i-Size, you can get R129 certified seats that aren't i-Size, but they are very rare, so we will continue to call them i-Size for this guide).

These are collated by the height of you little one which is a much easier way to determine which sea they should be in. We split these into the following categories: Baby, Toddler and Child. This is due to the fact different suppliers specify different heights for their seats, so this is the neatest way to group them.

Babies in R129 i-Size seats need to stay rear-facing until they reach 15 months old, but we always recommend keeping them rear-facing as long as you can as it's a much safer way for babies to travel.

Differences between R44/04 and R129

Feature R44/04 R129/i-Size
Impact testing Front impact testing @ 50km/h
Rear impact testing @ 30km/h
Front impact testing @ 50km/h
Rear impact testing @ 30km/h
Side impact testing @ 30km/h
Test dummies P dummy used in crash tests with 4 sensors Q dummy used in crash tests with 32 sensors
Direction of travel Forward facing possible from 9kg (approx 9 months) Rear facing mandatory until 15 months
Classification Based on child's weight Based on child's height


The next thing to consider is will it fit in your car – not all seats will fit in all cars. Check your vehicle handbook, this should have a section on what child seats can be fitted in your car, and whether you have any features like ISOFIX, top tether points or underfloor storage which will affect what type of seats can fit your vehicle. One of the benefits of i-Size seats is that if you have a i-Size ready car you can be sure an i-Size seat will fit.

Most supplier website have a vehicle compatibility list so you can easily check to see if the seat you are looking at fits your car. Also think about if you planning on swapping the seat between cars – does it fit both cars?

Other things to consider

  • If you are buying an infant carrier, do you want to use it on your pushchair frame? You will need to make sure it is compatible.
  • Do you want to fit the seat on a base? Do you want a base that will fit the next stage seat too?
  • Do you have ISOFIX points in your car?
  • Never buy a second-hand car seat – this isn't because we want to sell you a new one, it's because you don't know the history of the seat and it may have internal damage (even from being dropped) that you can't see but makes it unsafe!

Rearward or forward facing?

People are often very keen to have their little one facing forward in their car seat as soon as possible but this is often not the best way! Due to the forces that happen during a frontal crash, keeping your little one rear-facing as long as possible is best for them. Baby's heads are disproportionately heavy in relation to the rest of their body and their neck muscles are not fully developed and this type of crash puts unnecessary strain on their delicate necks – in fact in a forward facing seat a crash at 35mph, their neck would be subject to 300-320kg (47-50 stone) of force, whereas in a rear facing seat it would be the equivalent of only 50kg.

Rearward or forward facing?

In fact, some car seats will let your little one rear face until they are around 6 or 7 years old.
You might worry they don't have enough room for their legs, but they do!

Jargon Buster

  • 23-25kg Harness: This is a car seat with a harness designed to be used for longer thanks to the increased weight limit.
  • 3-point belt: A standard vehicle seatbelt with one part that goes over your shoulder and torso, and one part that goes across your lap.
  • ADAC score: This is a test carried out by Allgemeiner Deutscher Automobil-Club (German Automobile Club). Not all seats are tested and the seats to test are picked by ADAC themselves. The score they are given donates how safe they consider it to be, with a lower score being the best.
  • Backless Booster: A booster seat designed to raise your child, so they're positioned correctly for a seatbelt. Smaller and slimmer than the high-backed alternatives but offers no additional protection.
  • Base: This is a separate piece of the car seat that fits in the car and the seat clicks onto it making installation easier – fitted using ISOFIX points, they can sometimes be used for second stage seats too.
  • Buckle Crunch: The term used when a seat belt buckle is pulling against a car seat and negatively affecting the installation.
  • Combination Seat: Used to refer to any seat that covers multiple groups, but most commonly 0+/1 and 0+/1/2/3 seats. These can vary a lot, with some options being rear and forward facing, or with others being only forward facing.
  • Extended Rear Facing (ERF): This is where a seat offers rearward facing travel as an option over and above the mandatory for that type of seat eg R44/04 seat - 9kg, R129 seat – 15 months. Widely considered the safest way for your little one to travel.
  • Forward facing: A seat where the baby faces towards the driver.
  • High Backed Booster: A booster seat that features a high back that offers head and shoulder protection as well as positioning the child correctly for a seatbelt.
  • Impact Shield: An alternative to harnesses, an impact shield is a big cushion that's held in place with the seatbelt. This allows your child to have their arms free, but still be safely contained in the seat. They're also very good at keeping in budding escape artists!
  • Infant Carrier/Baby Car seat: First stage car seat that can sometimes be fitted onto a pushchair.
  • i-Size: Part of the newer R129 regulation, it's designed to make fitting in cars easier, especially if you have an i-Size ready car.
  • ISOFIX: A simple method of car seat installation allowing you to click and go. The bars on the back of the seat click into special sockets on your car and are generally using in conjunction with a support leg or top tether. ISOFIX is a standard feature in most cars post 2007, but always check your handbook.
  • Lap Belt: The part of the seat belt that goes across the lap, sometimes used to refer to older seat belts that are only 2 points – very few car seats can be installed with just a lap belt.
  • Rearward facing: A seat where the child faces towards the rear of the vehicle.
  • Rotating seats: These seats turn to face the door of your car allowing you to get your little one in and out of the car easier.
  • Shoulder Belt: The part of the seat belt that goes across the shoulder and torso.
  • Side Impact Protection: Not every R44/04 seats undergo side impact testing, but some do, and all i-Size ones do. The impact protection can be something as obvious as an additional piece of seat you add to the side closest to the door, a something you flip or twist out of the side of the seat or it could be something invisible built into the shell of the seat.
  • Support Leg: This is the leg that extends from the base or seat and braces the car seat against the floor of your vehicle to stop vertical movement. These are usually incompatible with vehicles with underfloor storage.
  • Swedish Plus Test: Sweden are the world leaders in child car safety and have the toughest crash test in the world. Some car seat manufacturers choose to put their seat forward for this optional test – it crash tests at higher speeds and uses a much shorter braking distance (the shorter the braking distance, the greater the deceleration and, therefore, the more intense the forces received in the impact). The seats that have passed this test are considered to be the safest on the market.
  • Top Tether: This is a strap that usually goes behind your vehicle seat to attach to an anchor point in your vehicle (most commonly halfway up the back of the seat but can be at the bottom of the seat or even on the boot floor) which prevents the car seat from moving vertically. Not all ISOFIX cars have top tether anchor points, so always check your handbook.
  • Underfloor Storage: Some vehicles may have small storage areas in the floor in front of the rear passenger seats. This is typically incompatible with support legs as putting them on the lids is at risk of shattering in an impact. Always consult the instructions and vehicle handbook as it may be okay if the storage is filled with an approved block, or if the leg can reach the bottom of the storage area.