Boxing gloves. It's appropriate in the context of the story. But still, the covers in this series ... or rather the re-release of this series ... are hideous.
Oh, and I wish people weren't judging these books by their awful covers, because the stories are quite good. But, yeah, no one will read them because of the atrocious covers.
Oh, wait. Even knowing what it is I can't figure it out! Time to remember "Never judge a book by its cover."