Millennium ratchet seat back Code - MRSB/RAT1/216 - Click here to enquire Millennium ratchet seat back Code - MRSB/RAT1/255 - Click here to enquire The Millennium Ratchet seat back differs from the Rips as it is does not come with a cushion and therefore is not a seat. It will secure a manual wheelchair only and provide the wheelchair passenger occupant belts. There are two variants available. The first locates into tracking with 216mm pitch. The other locates into 255mm pitch. The latter was designed so that it could be used in the tracking left on the vehicle when a stretcher is not being used. (NMI stretcher lock clamps locate in 255mm pitch track also) see stretcher locks.