Umarex C88 Umarex bottle adapter

C88 machining bottle adapter, no instructions or info parts just came in a box. What is the metal shims washers for? They are different thicknesses, are they for clocking the adapter so the valve and gauge can be timed how you like? Also, can a 500cc bottle fill a 500cc bottle? Does the fill bottle have to be higher pressure than the bottle I'm trying to fill?

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