Bucky recoiled back slightly, mind already whirring on how he could phrase this without upsetting Tony who could be pretty damn sensitive if he thought that a gift was being snubbed. Because the arm was amazing, it really goddamn was, he was just... he was scared about more medical procedures, or having something attached to him, or-- all of this crap.

"Uh-- okay, we can try it."

He scrubbed his hand through his hair, brow furrowed.

"But I can take it off if it freaks me out, right?"

Hopefully that would be okay. It was an admission of Bucky's vulnerabilities, rather than an attack on Tony and his generous gift.