Finally, an inexpensive, foolproof system for sizing ring & pin combination tube plugs. The two piece tube plug has long been the tool of choice for isolating ruptured tubes due to its extended sealing area and its resistance to "overdriving". The only downside to using this plug, over the standard tapered plug, was that the ring portion had to be accurately sized to the tube I.D.. This sizing operation requires the tube I.D. to be measured to the thousandths of an inch with a precision measuring instrument.

Tools for Industry, Inc. has developed a foolproof and easy to use solution for this problem... the TFI TPS line of gages. These gages cover the popular ring sizes for 5/8" to 1" O.D. tubes with wall thicknesses of 16 through 22 BWG. All gages have  machined diameters that cover the popular ring sizes. Diameters are stamped with a number to identify its relative ring size.

To use simply insert the gage until it will advance no further. Withdraw the gage and note the number on the last diameter to enter the tube. Order the two piece plug with the ring marked with the same number.