Originally Posted by BEC

Maybe not quite as rare or unusual but something I stumbled over after starting down the rabbit hole that Joe's post showed me: https://www.ebay.com/itm/3343449603...AAOSw0w1hs~b N

Not my listing, I don't know the seller. Appears to be a Boy Scouts only bulk kit from, I'd guess 5-10 years ago. I don't think I've ever seen that plastic BT-20 to BT-50 transition before in anything else. The overall design reminds me of another one (whose name escapes me at the moment) but which was BT-20 to BT-5-based.