I received 19mm 6:1 heat shrink, which took two weeks to arrive ( damn Covid!!! ). I installed the heat shrink on the rudder cable ovals. The cable attachment bushes on the rudder pedals and rudder are a different size. The 6:1 heat shrink is much thicker than I was expecting, but will do the job very well. Now all I have to do is climb under the instrument panel to reattach the cables.