sway bar sizing???? HELP PLEASE

hey whats up me again.... im all into this whole sway bar thing, please read the post previous to this one... if you have not already...

whats up with all the sizes in sway bars???
someone level with me and tell why are there 13mm 17mm 19mm 22mm and 24 mm???

which on is the best for a civic 2000 (4 Door)

some say the OEM bar is the way to go, and other say that aftermarket is the way to go.... >???????????????????????? what does what???
HELP LOL

for a rear sway bar anything over 17mm will tear your sub frame. To be cost effective your should get a si rear sway bar.