Never had great genetics there. Half decent size but not much definition, usually hung around 17 inches. In the past I did arms on their own separate day. A routine would consist of three bi exercises and three tri exercises, doing a bi exercise for four sets, then a tri exercise for three sets et cetera. Worked well enough, arms were still pretty proportional. But eventually realized that biceps are small enough and recover fast enough for hitting them twice a week. So after back day I would hit up three sets of 21's. No, not the gay ones with partial reps that you see frat boys doing. What I do is seven sets of straight bar curls, seven sets of hammer db curls, then seven sets of reverse cambered bar curls all in a row with no breaks. Pick a weight that allows you to get it somewhat easy on the first set since it will get harder on the next two. Or gradually decrease your weights as I do sometimes so that you go to complete absolute failure at the end of each set. After a couple months of that I've put on a solid inch on each arm and like the overall shape as well. One of these months being post cycle therapy (pct) as well. So try it out, might work for you.