I have one of the older Madbull adapters. It works fine with all my guns except my KSC Glock mags. Seems like the nozzle doesn't mate well with my mag valves. I can still fill the mags, but get a lot over 'spray'.
I just use the AI plastic adapter. Works like a charm on all my guns, comes with the silicone oil and a duster adapter, and is a Canadian product produced by one of our own forum members. Makes it an all around winner for me...