Why would I want to do that, even if I could? A TP tube (I'm sure they vary a bit) that I measured had an inner diameter of 1.75" (4.45 cm) or an inner circumference of 5.5" (14 cm). It would be impossible to get my hard (or even semi-hard) cock into a tube - my girth is over 6". And, if I managed to stuff my soft cock into the tube, what would be the point? Pumping up just the head? Breaking the tube? I think the only real purpose a TP tube serves is to illustrate in a picture whether your girth is over 5.5" (14 cm).