Single handle ball locks are either old Canadian tanks with the black plastic handles that were held on with two phillips head screws, or most new tanks with the curved metal handle welded on. Huge price difference. The old ones are fairly rare, almost all used ball locks will have the twin handle rubber tops, although, extremely rare are rubber tops with only a single handle cut through, I have only come across a few. If you want new, I have 3 & 5 gallon tanks on hand. Also have used Ball locks available, refurbed & pressure checked.