Rounded bleed hex screw

1. Slightly bigger hex key forced in.

2. Cut a groove in it and undo with a screwdriver.

3. Grab sides with pliers and turn.

Replacement through local bike shop or internet shop or tool factor that also deals in bolts or simple internet search for M4 flat head bolt. Or M3. Or whatever it is.

These are make of cheese - I've had issues myself and my bike shop has too. for a while the part was unavailable which says a lot...

I removed mine by using a Tx bit just a fraction larger. Grind or stone the end flat so it is 'sharp' and push it into the socket, then turn it while keeping the bit pushed into the socket. Mine broke free reasonably easily using this method.

SJS had some is stock a month back, I'd try them first.

In the future don't do them up very tight, use a high quality hex key (something like a Wera HexPlus or Bondhus) to remove them and maybe pray to your favorite deity.

It really is a poor bit of design from Shimano. I suspect it was done to limit the force used to do these caps up, but doesn't seem to have accounted for the caps binding in place and the increased force needed to undo them!

Good luck with that. To my mind the problem isn't only that the bolts are soft but also allen keys have quite a large tolerance. One manufacturers 4mm allen key is not always the same as another. If the tool is slightly smaller than the bolt then its pretty easy to burr the edges and then from there on in its a short step to the problem you have. Have a rummage in your tool box or some of your mates and you might find an allen key that is just a little bit larger than the one you have and that could do the trick.