Doing a clutch job on my 02 chevy p/u. Went to drain the trans and the drain/fill plugs are an internal hex. Couldn't find any bolts lying around the house to use as a "tool" that would fit. Mic'ed the hex and it's about 17mm which is the head size of an M10 HH bolt, which I picked up at work. No biggie, but it delayed the trans drain by a day. Why on earth would GM use an internal hex on those plugs? Is it because it's aluminum? If so, the 4x4 Xfer case drain/fill plugs are aluminum and they use an external hex that an open end or even a crescent wrench would work on. Just seems like every time I work on a vehicle, there's a need for an uncommon tool to do a simple task.