So what's the difference between the real steel Glock 20 and Glock 17 pistols? Larry Vickers is on hand to tell you on this episode of Vickers Tactical TAC-TV... "All Glocks follow the same design theme, regardless of the caliber, however you essentially have two sizes of Glocks. You have a 9mm in 40 size and you have a 45 in 10mm size. Larry has a Glock 20 and Glock 17 to show you the differences between the two."