One carriage here is listed as replacing Seaview™ rollers: a 38.6 x 15.7mm adjustable sliding door carriage and roller in stainless steel, which also suits Rylock® and Lidco® units of the same pattern. A stainless carriage is a coastal answer to a coastal problem, because the usual failure is the roller pin or the carriage body corroding and seizing, after which the sash drags in the track and the adjustment screw will not turn. The two figures in the title are what identify the part. Slide the sash out and measure the old carriage in both directions before ordering, rather than going by appearance, because sliding carriages differ by only a few millimetres and one that is even slightly oversize will not sit in the channel.