Sperm plugs?

I had my het pied male out today and was thinking back upon when I got him and couldn't remember if I had visually sexed him or not. He is around 800g and I figured he would not pop but I tried anyway since he seemed nice and calm. When I put pressure on the tail out came very thick white gunk. I can assume this is sperm plugs right?

Not necessarily, were you not able to pop him?

Yes its most likely sperm plugs, its much harder to get an older male to pop and most times you would see plugs before any hemipenes, totally normal.