I only had fitment problems with mine because, apparently, I got the first generation of their Violator mufflers - aluminized with about a 16" case. The newer ones are stainless muffs and have a shorter (14", I believe) case, so the length issue shouldn't be a problem, anymore ... or at least that's the present word on the matter.
Regardless, I have LOVED the sound of these muffs from the moment I first installed 'em behind my cat'ed UPR X-pipe (even though I hated the X-pipe, itself). I dunno how they'd sound with an H-pipe, but with the off-road X-pipe I'm now running, they're downright EVIL. They're actually quite civil in normal driving, they don't drone at cruise like Flowmasters, and up high they've got an angry, hollow-sounding rasp that reminds me more of Spintech muffs than Flows.
BUY THEM. You won't regret 'em a bit ... although you're gonna pay more than I did. (I scored mine at WFC9, $80 for a PAIR. HA!
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Pypes better start sending me some free parts or something one of these day, for all the pimping I do on here for their mufflers...