I just purchased my 370A large case for a VW GTI MK4. The Billet Tech has up to 320A in a nice case while the non Billet Tech goes to around 370A. What sold me was the low rpm high output of the alternator plus the 10 yr warranty. Singer may have a lifetime warranty but only offered a 240A for my car and Mike mentioned I might still have low rpm issues. I purchased my alt through this guys Fastlane Parts Supply - FastLane Parts Supply.