It's where you can try a bit & send it back for a refund if you don't like it.
I wanted to try a myler combination but they're £90 so an expensive mistake if my horse hated it after 5 mins, so I ordered it & then had 21 days to return it in its orig packaging if I didn't like it. They would then refund my money less £5 admin, or send me something else to try.
Luckily it's worked like a charm so I'm v pleased. It stops you ending up with a tackroom full of bits that you've only used once.
also www.thehorsebitshop.co.uk, they do Neue Schule, Myler, Sprenger etc. You pay £5 postage and £3 to try the bit, and if you haven't returned it in 28days you pay the balance, or you can return it and have another on trial. I like the fact that you get 28 days, there used to be one or two that did 14 days but that never seemed long enough.