Thought this was the TT rule for Superstock.

“ 29.11. Wheels from a previous model year and from the same motorcycle manufacturer may be used providing no other modifications have to be made in order to facilitate their use.
29.12. Alternative wheels must be of the same diameter, rim width and no lighter than those fitted to the homologated motorcycle.
29.13. Carbon Fibre / composite wheels are permitted only when fitted as original equipment on the homologated machine and have been certified by the manufacturer as “Fit for purpose” for racing use on the TT mountain course. Optionally, these may be replaced by an alternative ALUMINIUM wheel from the same manufacturer or an aftermarket racing wheel supplier. In any case they must be of the same diameter and rim width as the Carbon Fibre / composite wheel they replace and weight must be no lighter than the homologated composite wheels.“