It's small size, ultra-long burn time and low price make it ideal for divers requiring longer burn time without a larger battery pack, and an excellent choice for divers on a budget. Many divers believe the 18-watt lamp to be the most versatile of all, both as a dive light and a video light, the perfect balance of brightness and burn time. It is also the whitest of the lights. The 50-watt lamp is ideally suited for the most serious photographers and videographers who demand the brightest light available. It is also the de facto choice for divers who shoot motion picture film underwater.
G indicates a Goodman Handle.
MR indicates MR-11 style head. V indicates video reflector. W indicates Sartek's exclusive locking wetmate connection system. I have heard there are problems with wetmates. Sartek has developed an exclusive locking system which maintains a secure connection.