Hi Kev
I have had seals from two suppliers Northwest Classic twice and Automobileelectrics once.
The second supply from NWC the secondary seal was too big and eventually NWC agreed and sent me a replacement after I sent an old used sample.
I was still having problems occasionally of slow brake release and I investigated further and found that the control piston primary was suspect.
I noticed Automobileelectrics on ebay were selling sets of seals for the Girling MK11B, which I purchased,
These seals were the largest of the control pistons seals I received.
At this point I decided to measure all the seals I had in my possession and fit the smallest after an assessment fitting and testing by hand. The servo has been fine now for since April this year
After this long winded problem I now check and measure everything I can and take photo's because lots of spare parts are remanufactured for our cars.
Just noticed a new supplier of seals
https://www.ebay.co.uk/itm/Ford-Lotus-C ... 1438.l2649 They might be better sizes but the seller tells me they are manufactured to Girling spec.
New message from: slate-hall Top Rated Seller(2,190Red Star)
Hi, no these seals are not genuine Girling, you will find that in most cases original new old stock Girling and Lockheed seals shrink and go hard with age and that is why these seals are remanufactured to the original Girling specification, kind regards Andy.
Kev you get what you can today good luck