Matt Damon sent Ben Affleck and Jimmy Kimmel a fax of his butt.

The 43-year-old actor hit back at Twitter jibes from his close pals, who have recently teased him over his reluctance to join the social networking site, by sending them a bare-buttock picture.

The friendly teasing began when Jimmy - who often mocks Matt on his late night talk show 'Jimmy Kimmel Live' - shared a link to a charity auction that Matt and Ben, 41, are involved in.

Ben thanked Jimmy on his Twitter page, but the 'Argo' star couldn't help but include some gentle ribbing of his best friend.

He wrote: ''I thank you buddy. And @easterncongo & @water thank you. Matt on the other hand? Matt you there? Right. We will fax you.''

While the 'Elysium' star isn't a Twitter user, he caught wind of the mocking and sent Ben and Jimmy the humorous fax.

Comedian Jimmy shared the fax - which Matt sent on a letterhead belonging to his and Ben's production company, Pearl Street Films with his Twitter users, writing: ''.@BenAffleck - did you see what your 'friend' Matt faxed to us? NSFW (sic)''

The fax reads: ''Dear Ben & Jimmy, here's my fax. Love MD.''

The hunky star signed off the correspondence by putting his own spin on Twitter hashtags.

He wrote: ''Faxtag: KimmelHasManBoobs (sic)''