you may be interested to know that new focus rings are now available. I have them done with the help of Movie Camera Support in London, which you may contact for any inquiry regarding the rings.
Solid material has been used, same as the Preston rings. The rings are secured on the focus knob through the original Bartech screws. They've already been tested on different sets, a joy for the focus puller, no more messing around with strips, prepping days are now a breeze.
I think is the perfect add on for the much trusted Bartech kit. MCS is based in London, but they can ship the rings anywhere; they are ready to accept Credit Card payments. Price for the rings is 16 British Pounds each.
Please refer to Movie Camera Support directly as I'm not involved in their business in any form, I only helped them with few hints on the conceptual side and tested the rings on the field.
You can contact Simon or Dave at: firstname.lastname@example.org
All the best