First question - On the center of the piston there's a rubber button that plugs a hole. What's that for and could I use that caliper without it? One of the calipers I got from Napa has it missing. Second Q - The brake pads that came with my calipers have a little stub on the back that fits into an indentation on the piston. When I need to buy replacement pads do I need get caddy pads or can I use the spare D44 pads I have? Last Q - What keeps the pads from rattling? The D44 calipers have the clip that holds the pad to the piston. The caddy caliper doesn't have anything. It looks like the pads will be loose and make noise. Anyone have a problem with that?