Chicco - Synthesis XT - Plus Car Seat Synthesis XT Plus car seat has new fabric cover with extra padding for a more comfortable ergonomic sitting position. It has padded shoulder straps and buckle and a new sunshade. The car seat is approved to standard ECE R44/04 for Mass Group 0+ (0-13 Kg). It is fitted in the car with a 3-point safety harness in a rear-facing position and it should not be used in cars with air-bags.