Now, That I actually own one(Disco) , I can accurately calculate the number of fills and shots I can get from my scuba tanks. With the 30cf tank (weighs approx. 15 lbs.) filled to 3100psi , I can get 120 fills with my Discovery at 35 shots per fill, that produces 4,300 shots from a $7 fill on the scuba tank. With my 88cf tank filled to 3300psi, I would get 368 fills for a total of 12,905 shots for a $7 scuba tank fill. Wow !! And these can be had for approx. $200 for tank and fill gauge yoke or about the price of one of the cheaper pumps. kirby