The BXpanded thumb might be OK on a BX series tractor. I looked at the BXpanded thumb for a B Series tractor, and was just about to pull the trigger until I found this video. I have a B3030 with a BH75 and installed the Kubota manual thumb. I had to fabricate the dipper arm mount because the BH75 doesn't have one. The Kubota thumb is really nice.
