What size tool for manual tranny drain plug?

[wyomingwapiti]

Used to be a K5 owner. This is a great forum site. I need an answer for my current truck that I cant seem to find on other sites. I now own a 1996 GMC K1500. I was going to change out the manual tranny fluid today, but didnt have the correct size tool to do so. What is that thing anyhow? A torx head? If so...what size? Help

 

[pvfjr]

Hmm, been a while since I've seen a 90's rig...