Oil Rigs came in 2 sizes originally when first invented. The classic standard 14 mm and the oversized 18mm. When smoking wax, if the product is of high enough quality you only need a small dab, that is where the name " DABS" or "DABBING" comes from. The 10 mm oil dome and domeless rig was invented because you dont need a big hit when the product is an excellent quality. 10 mm not only is very small and discreet, but also can do small and powerful fast hits. I highly recommend when purchasing an oil rig, ( if you know what good wax is) to purchase a small portable rig, that can go with you practically anywhere, from the car (fitting perfectly in the cup holder) to the comfort of anywhere in your home, my personal preference is my bed, nothing like dabbing at home and listening to some soothing music! I was just speaking to my brother and he took 2 dabs at 11 am and he is still on some wacky tabacky not that its a good thing since he forgot my coffee that I asked for about 15 times at least. Not saying that this will happened to you but it is something that when you do not know your dose you can abuse it.