The 4912 will fit a 1/6th and a corny, but not 2 1/6th's. It's also easier to get a low profile sankey coupler. There is not a lot of extra headspace in the 4912
If you look on ebay you can find refractometers for about half the price you see at morebeer, northern, etc. I picked one up for $32 shipped and it is working out perfectly!
