Attached are pictures of a 1lb bat weight we bought at a local sporting goods store. Last night I cut it in half and drilled two 10.2mm diameter shallow holes in each face. Glued a 10mm magnet in each end voila - homemade autopilot buddy. You might put a little fingernail polish on the ends to keep them from rusting. I think it's powdered metal because my drill wouldn't pull a chip, it just pilled out. If I do another one, I'll probably use a 10mm end mill.