Don't use those for a bowl. Those aren't open all the way through. Those are hex head sockets that slide into a drill or wrench. You want a socket that's open all the way through or else the smoke won't go through. You want something like this for the bowl...
Best thing to use for a bowl and downstem (besides a store bought one) is a trumpet mouthpiece. Works like a charm.
I used a socket. It's 9mm and I got a zebra mechanical pencil. I took it apart and the metal tube fits almost perfectly into the socket. Just use duct tape or electrical tape to make sure they're put together well. If you want to make a slider bong, get a sharpie then grab some wire cutters or whatever to pull the thing apart. Cut like right above the circle emblem on it to make it fit with the zebra tube. Its pretty hard to cut through the sharpie so just put a lighter to a knife for a while and push really hard onto the sharpie tube. It slides straight through.