I assume you send a fragment and the receipt or something, otherwise you can smash your klein bottle into many fragments and the return policy becomes a bulk discount.
(Though this particular business seems low volume enough that you can probably easily deal with that problem so long as you don't have to scale it.)
To my surprise, I haven't found anyone breaking their bottle on purpose. (or on a porpose). One of the nicest things about running this micro-business is that, sooner or later, I'll meet most of the people who own a Klein bottle. The math & physics community is a wonderful place...
I’m not really part of the math and physics community, but I just wanted to say I’ve been delighted by everything I’ve ever seen that you’ve done. You make the world a more interesting and fun place.
It's both an honor and a joy to find myself a member of several impressive communities ... old-style hackers, math & physics jocks, people with solder-burns on their fingers, and left-coast techies.
(Though this particular business seems low volume enough that you can probably easily deal with that problem so long as you don't have to scale it.)