This 2 in 1 tube cutter has two functions. The reverse of the tube cutter has an 8mm jaw that can be used to pull the coller back on the various Duotight and John Guest fittings.
The tube cutter itself has hardened and extremly sharp blade that makes nice clean and square cuts on tubing. This is also perfect for using with the Duotight and John Guest fittings.
A clean, square cut is essential non building a leak free system.