The technical difference is the FBV uses straight slopes down to the flat on the inside edges whereas the BFD uses a slope with a radius down to the flat. |\_/| versus |(_)| Blackstone came out with the FBV well before Blademasters BFD. Blackstone (per JR) tried different cuts (including the radiused slope like the BFD), but found that the V profile worked the best. Blademasters has a document on their page discounting the blackstone FBV claims... it's an interesting read, but read it for what it is, a marketing tool. In fact, blademaster went to great lengths (prior to the release of BFD) of trying to make people believe that flat bottom profiles were merely a gimmick. Simple fact is FBV is much more prevalent and I have yet to see a negative review of it. Can't argue with success. Someone on another board managed to call it a scam lol.