Immediately after receiving the package I tried it in the boots I have that are too narrow. Though both stretchers fit into the boots fine, one of the plastic universal joints on the screwing mechanism broke immediately upon starting to screw the stretcher open and I had to continue screwing with my hand.<br /><br />I'll update this after the boots have stretched for a few days or when I hear back from the merchant about a return or replacement, but the bottom line is that there shouldn't be a plastic part on a high stress mechanism in the first place.