This thing is a god sent. I own 4 nice Seiko straps that come with deployant buckle. Seiko deployant buckle is a pain in the wrist for me, as the end curve where the buckle folds doesn't sit right on why wrist. I couldn't use those nice leather straps because of that.
This butterfly deployant buckle, on the other hand, sits perfectly on my wrist, right in the middle. Unlike what the other reviewer said, I never feel there's any sharpness with this buckle. Perfect fit! For reference, my wrist is 6.5".