Car Seat Glossary

When searching for child car seats online, the different sizes and terms can quickly become confusing. This glossary breaks down the key terminology to help you make an informed choice when selecting the right car seat for your little one.

R129

R129 is the newer safety standard that is gradually replacing older sizing systems. R129 seats are chosen based on your child’s height and encourage rear‑facing travel for longer, until at least 15 months old.

R129 seats come in three main height categories:

• 0–85cm – rear‑facing baby carrier or baby seat using a harness
• 0–105cm – rear‑facing until at least 76cm, then forward‑facing
• 100–135cm (UK) / 150cm (ROI) – forward‑facing child seat

R129 vs i‑Size

R129 and i‑Size are often used interchangeably, but they are not the same.

• R129 is the overall safety standard.
• i‑Size is a category within R129 that focuses on compatibility with ISOFIX anchor points.

All i‑Size seats meet R129 requirements, but not all R129 seats are i‑Size. Many i‑Size seats include an “i” in the product name or display the i‑Size logo.

ISOFIX

ISOFIX is a universal fitting system that uses built‑in attachment points in the car rather than a seatbelt. This reduces the risk of incorrect installation and helps secure the car seat more easily and safely.

Impact Shield Technology

Impact shields (also known as safety cushions) fasten around the front of your child while they are in their seat. They work like a pre‑inflated airbag, spreading the forces of a collision over a wider area to reduce strain on the body.

Group

A “group” refers to the category your child falls into based on their weight or height. Example: Group 0+ = Birth to 13kg / 0–85cm.

Rotating Seat

A rotating or 360° seat allows extended rear‑facing and forward‑facing travel. It also makes it easier to lift your child in and out of the seat.

Multi-stage Seats

Multistage seats grow with your child and can be used across multiple stages of development. Some are suitable from birth up to around 4 years, while others last from birth until your child no longer needs a car seat.

All-stage Seats

An all‑stage car seat is designed to grow with your child from birth all the way through to when they no longer need a car seat. It adapts across multiple stages from rear‑facing for newborns, to forward‑facing for toddlers, and finally to a high‑back booster for older children.

Top Tether

A top tether is an additional anchorage point used on some car seats. It is a strap attached to the back of the seat with a hook on the end. When tightened correctly, a green indicator will show. The tether point may be located in the boot, on the back of the vehicle seat, or in the roof, and is marked with an anchor symbol.

Support Leg

Many ISOFIX seats and some belt‑fitted seats use a support leg to prevent the seat from rotating in a crash. The leg extends to the vehicle floor and provides extra stability and rebound protection.

Types of Car Seats

Carrycot

A carrycot allows your baby to lie flat in the car. These are sometimes called side‑facing or lie‑flat seats and combine the safety of a car seat with the comfort of a carrycot.

Infant Carrier

Infant carriers are rear‑facing and place your baby in a semi-lying‑flat position. They can be removed from the car with your baby still inside and are often compatible with pushchairs.

Car Seat Bases

Car seat bases attach to the car’s ISOFIX anchor points. The infant or child seat then clicks into the base. Bases are typically compatible with Group 0+ and Group 1 seats. Some seats attach directly to ISOFIX without a base, so always check product details before purchasing.

Toddler Seat

Toddler seats are the next stage after an infant carrier, although some multistage seats can be used from birth. They may be rear‑facing, forward‑facing, or offer both options.

Child Seat

Child seats are designed for children who have outgrown a toddler seat. They raise your child so they can safely use the car’s seatbelt.

At Halfords, we stock a wide range of child car seats from trusted brands such as Joie and Cybex. Explore our range online to find the right seat for your child.

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