These are new custom made hi speed needle valves for the RCV, Asp, and Magnum XL 4-stroke engines which use this stile of needle valve. Please look at picture and see if this is the stile you need. The RCV engine is compatible for all the full production engines, CD and SP. These will also work on all the Magnum XL and ASP 4-cicle engines, from the little .30 to the large 1.8 They will also work with most (but not all) of the larger .40 and larger 2 strokes. Please contact me for more info before committing to purchase to make sure this needle is compatible with your engine. These are custom made and I only made a few and will not make any more.