Well it depends on the size of your cock and the size of the tube. Lets say erect your cock just fits in the tube with an 1/8" all the way around. You start pumping 2-3 hg and you will notice that your going to get thicker at the base of the tube. You slowly gain from the bottom until your fully packed. I started with a tube 2 1/4" wide, it was too wide, and I was not gaining much in thickness. So I bought a 2" tube, and now after several years packing about half way up the length of my cock. Now I pump for 10 minutes, then massage and take a break for several minutes. Then repeat for over an hour, then I have a nice pfat cock. I hope this helps you?