20mm refers to the piston size. OD of tube is 24 or 25mm. What you're grabbing with the tool is the notches in the 'cup' in the case of OE and that's like 30mm (wag). The K-Tech has nothing similar to grab. The nut used to seal the top of the cartridge has flats on it but I don't know off hand the width, probably 17 mm.Am I right in thinking that if the stock and the Ktech are both 20mm cartridges, I can get some 22mm OD, 20mm ID pipe to make my holding tool?