Bad move TVT - you've lost a lot more than $70 on this deal by turning into a pissing contest.

The mechanic most likely took it apart with a "it's gotta fit somehow" effort that's human nature. He was actually giving your company credit believing it MUST be the correct part or you wouldn't have shipped it out !!

Count me as one of the members that won't be buying anything from you. To make someone "fix" a part with a special tool only you have is very arrogant. This never would have happen if you sent the right part to begin with.

Do the right thing and ship him the correct part, accept the incorrect one in its present condition, and refund his shipping costs. If you do that, there's no need to refund his entire purchase.