im getting a bit ahead of myself considering Im in the middle of my first cycle now (test e 500mg/wk for 12 weeks) but I'm always contemplating my 2nd cycle for next spring. Right now I'm thinking test e @ 400 - 500mg/wk with one of these two. Primo at 500mg/wk along with test at 500mg/wk is VERY tempting!
with my primo cycle i ran I experienced "definition" in my legs, biceps and chest that i had never had. i wouldn't call it mass gain.. if you want mass look into a deca/dbol/test cycle. that is a pure mass cycle. just make sure you set up a solid PCT and run cabaser while on.
Primo is my favorite for making slow and steady muscle gains. Anavar made me so hard and gave a great pump feeling. When stacking both of them together you have a sick ass cycle.