Hipshot BT1 bass Xtender key for any/all Musicman basses. Hipshot has these on backorder. I waited two months to get this one through Bass Parts Resource. Cost over $90. In the meantime, I decided to just get a five string. Never used, in original packaging. Somebody buy this off me. Turn that Stingray 4 or Sterling 4 into a Stingray 4.5!