10 Pieces Mini Nylon Ball Transfer Bearing Unit Table Conveyor Roller Ball for Transmission, Furniture,Wheelchair 1/3inch

Q: how do you attach these ?

I hot glued them to the bottom of what i need them on for a quick fix. Probably for the best looking result and performance, you could drill a hole and press fit them in with a bit of glue. It will probably depend on what you want to use them for. There really isn't an included adhesive or instructions

Q: What is the height of the plastic housing? Specifically what depth hole do I need to drill to fit these into?

If you are limited for space, 5/16" is the minimum depth. 3/8" will give you plenty of clearance.

Q: Is there any metal in Theseus there any metal in these

If the question is, "Is there any metal in them?" No, they are all nylon.

Q: Can the ball bearing be temporarily removed, either the all-nylon or the nylon + steel version?

Even if you could, I suggest you don’t because even if the bearings housing survived the prying , it would most certainly be warped if not outright damaged.