The W1i Tillett car seat is extremely narrow yet it can still accommodate a majority of drivers. You have the choice to order a 40 or 44 cm front. The two specifications remain the same size internally. The 40 cm version is made to allow fitment between the gearbox tunnel and the door sill. A 40 cm front will fit a Caterham, Westfield and most other similar narrow vehicles. With the 44 cm version the rolled edge is left on giving a more aesthetically pleasing line to the edge of the seat, therefore if you have the room go for this model.