YOKOMO SLF Big Bore Shock Set (4Pcs) For YD-4 (Y4-SBBS) Optional parts for YD-4, a super low friction aluminum big bore shock set. Wider cylinder diameter than a conventional shock and the length is also a new design for drift. Cylinder will achieve a smooth operation as much as possible from the Kashima coated treatment. It will also absorb some common micro-vibration from resin-made tires, leading to increased traction. NOTE: Springs and Shock oil are not included