Like the DIN pressure checker, these are surprisingly useful, saving having to dig around for a set of regs when you want to check tank pressures, and with less bits hanging off it.  Like most yokes, they are rated to 232bar, and there are different options depending on your budget and how cool you like your gadgets.  The pneumatic versions are pricey but very difficult to source and let you connect/disconnect in literally a snap - useful if you're checking a lot of tanks in the back of the shop before a big bunch of customers comes in.  They are available separately for your tank filling hoses.