Tyson Beckford -- Special Dong Delivery ... Bumpin' For Chippendales

Supermodel Tyson Beckford let his ding dong dance during his stripper debut with the Chippendales dancers ... and you may need to take a seat.

At 44, Beckford is probably twice the age of the other guys, but he held his own during practice, and really got the crowd going during last night's preview. Fair warning: this video may mesmerize ... think snake charmer.

When you snap out of it, you'll be happy to know he's the celebrity guest host for Chippendales at the Rio Casino in Vegas now through May 24th.

Sources say in the show he drops trou twice and it ALL COMES OUT ... but he cups it.

Of course we still have our favorite.