The HQ on my Maxxas is a push in. There were two HQ's. The newer, more common one has the baseplate rounded over on both treble and bass sides similarly. The one I have looks the same on the bass side but on the treble side there's an "s" curve, sort of an indentation right around where the arm goes in. Maybe that's the difference. Maybe all the ones that are rounded on both sides are screw in. I have an old Maxxas brochure that shows my tremolo in all the pictures, and on the back it reads: "The stainless steel, low profile bridge has hardened steel pivots. Push-in tremolo arm for easy removal." In the '89 catalog it shows the regular HQ trem, but doesn't mention the arm type.