This little oddity has been in his act for years. Again it is one of the hundreds of gas he has in his act and can be done offhanded and at any time. In the middle of any trick, story or bit you quite simple can appear to pull a varicose (or any) vein right out of your leg. Yes you just reach down and pull that sucker out! Another great laugh in Dave's act!
As with all his gags these are individually produced and made. Size isn't an issue unless you are XX large in the leg dept. Inform if so.