Bought these at hay days at the last second and just wanted to leave so I didn't pay much attention. *What are they?

The package says Woody's GDP-8500. *It appears that the last digits on woody's studs represents the length of the stud. *I have never seen a woody's .8500 stud. *So what size are they and how do I know if they are 5/16 or 7mm?

Measure the head diameter and shank diameter. * GDP is their (Woody's) 45 degree modified gold digger push thru. *Not too much use for .850 anymore.

So are these old studs?