The advice above isn't very good. You'll want to study up hypertrophy, and, in particular, on sarcoplasmic hypertrophy. Specifically, what that tells us is what common sense does: when you pump it up, it becomes bigger.
You defeat your goals, and, risk injury, when you lift at low reps. You're much better off to do higher reps. I'll leave it to you to read up on hypertrophy and make your own INFORMED decisions regarding training method. myofibrillated hypertrophy will make you strong (low reps) but you're looking for size and you want sarcoplasmic hypertrophy. This is something you'll need to study up on your own. There's lots of good information all over the place online.
If you look at guys with big arms, and big legs, you'll see that they all do medium count rep sets, and do them fairly often. Strength and size are very much different things when it comes to lifting / resistance exercise.
Understand that some folks have shorter muscle insertions and that makes their muscles look more "peaked." Also, understand, that some folks are leaner, and that can give a different look. Still, others have injury, or imbalances, that give them the "Popeye" effect (indicating a torn bicep). Further still, folks on stage often use "pump and pose" or methods similar , to accelerate sarcoplasmic hypertrophy. I.e., they inject fluids into the fascia around the muscle and shape it the way they want. In competitive bodybuilding, it's a given. The trick to size is NEVER low reps, but, rather, enlarging the muscle fascia, either by pumping it up with moderate to high reps, or by injecting into it to stretch it like a hotdog casing would. When exogenous fluid is injected into the fascia, the muscle has room to grow into that space (no hormones involved; just a fluid displacement) and the change in shape, and size, is pretty much permanent unless the person becomes sedentary. "Pump and pose" is part and parcel in competitive circles. The muscle is real, it's just that the space was expanded at a faster pace than normal and the muscle grew into it without any hormone, etc. Of course, site injections are like any invasive procedure and need to be approached from a very informed position and proper risk management / sterile procedure. You probably shouldn't do true "pump and pose" with silica, but, rather, something like grapeseed or cottonseed, if you venture down that path.
It's a MYTH that low reps produce size, and it's real bad advice to say so. Size is a function more of local muscular endurance. Do your research folks.
The advice about triceps is sound. Triceps are about 2/3 of your arm size.
The point: Moderate to high reps (avoid low reps to avoid injury and to hasten size gains) and be sure to work both sides of your arm.