Bottle Valve

Does anyone know is an NOS valve will fit on other bottles? Particularly NX bottles.

Yes it should fit. A bottle is a bottle (except for the weird ass zex bottles) and the hole is the same

why would you want to step down on flow,
The NX Lightning 45

the first nitrous specific valve ever produced in light weight aluminum. Manufactured from 6061 T6 billet aluminum and pressure tested to over 10,000PSI to assure your safety. The Lightning 45 will outflow any valve on the market today by a factor of four (excluding the NX DF5 valve). Restrictive bottle valves will no longer be a problem in the nitrous world. Includes a gauge port and push port. This valve will retrofit to any brand nitrous system. "
and if you want the DFS here it is as well

Thats what I put on my "other brand" bottle the lightning. When I go to powdercoat my bottles I will upgrade my NX bottle to the lightning valve too.