This is a replacement O.S. Complete Piston/Sleeve/Rod Assembly. This is a direct replacement part for the O.S. Speed .21 nitro engine, but is also compatible with the ProTek Samurai 321B engine as well!
This includes not only the piston and sleeve, but also the connecting rod, wrist pin and wrist pin clips. In fact the rod is already pre-assembled for you, so you can simply install it in the engine and forget about the hassle of removing wrist pin clips to install a new rod!