Blue Ribbon Motor Coach SpaceMaker Parts DUAL CYLINDER ROOM EXTENSION – 24.0" STROKE (WITH SYNCHRONIZING CYLINDER) MECHANISM AP20991 AP20992 AP20990 KIT (Part Page) CYLINDER ASSEMBLYITEM 1 – RAP15252 (24.50" STROKE) REPLACES AP15252 SYNCHRONIZING CYLINDERITEM 3 – RAP39271 (9.685" STROKE) REPLACES AP13224 and RAP90472 TUBE KITITEM 2 – RAP90480 – REPLACES AP13252