Takeo Spikes -- Guess What I Use My 20 Inch Neck For ... (Hint: It's Not Football)

Ex-NFL star Takeo Spikes is famous for an unusually large part of his body ... and he tells TMZ Sports, the ladies go crazy when they get their hands around it.

The former Auburn linebacker was at the LASEC event in the Pasadena Convention Center ... and we asked him just how big his enormous, veiny neck really is.

Spike told us it's about 20 in. around ... and if you're feeling a little self-conscious, Takeo says he's thinking about making a self-improvement video so you can increase your size too.