This is what they look like:

They're just a tad bit larger in diameter compared to a #6 washer, and maybe a 1/4 of an inch thick. The construction for these is almost exactly identical to the safer style slugs in Ryan's thread.
First, burn a hole large enough to fit your bushing into. It's important to make this hole as centered as possible.

Next make sure your bushing fits into this hole, if you're inexperienced/unfamiliar with the size of the bushings. The bushing should be flush with the front of the dart:

Finally apply a felt pad to the front of the dart.

After testing these, the darts seem to fly just as straight as slugs if you're proficient at centering the bushings. The ranges also seem comparable to slugs, but in my opinion, these hurt noticeably less. Feel free to post any questions about the darts! No I did not find a McM equivalent of these BUT they may be purchased here!
Edited by erich76, 26 August 2012 - 10:47 PM.