So I picked up a used racquet that was already strung. The seller told me what was in it, but I wasn't familiar with those strings so for the heck of it, I broke out the calipers (Sorry, mine are inch) and measured each string at 10 random spots: Wilson Kgut 17: .44 to .50 Mains TCS17: .46 to .47 X's Then I measured what I have packages of: Gamma Syngut 18: .45 to .46 Black code 17: .48 to .50 (All measurements were .50 except the one .48) Black Magic 16: .50 to .50 Spin X 16: .49 to .51 Hollow core 16: .51 to .52 Gosen 15L: .53 to .54 So all in all, there were 2 surprises: Black Code 17 was the same as all the 16g strings in my bag (how exactly would one measure a hex string anyway?), and the TNT2 18 seems to be only marginally smaller than the 17g strings. Also intersting to see the mains in the strung racquet varies quite a bit whereas the cross did not. So I measured another racquet: Black Code 17 mains at 57 lbs and 4 hours: .48 to .49 Gosen 15L x's at 55lbs and 4 hours: .51 to .52 So compared to the string in the package, the black code hardly changed size, but the gosen seems to have "streached" down a bit. In the end, I'm wondering how marketing is affecting the "size" of a string....??? especially in the case of the black code 17g.