These make a nice upgrade to the 924 or 944NA.

I have 2 fronts and 1 rear for sale, all from 86 944 Turbos, with all hardware, brackets, links & bushings for $50 each plus shipping.

The fronts are 24mm hollow.
The rear is 18mm.

First one to buy a front bar gets urethane & polygraphite bushings (used, of course).