Hi all, Over the years I've always rebuilt MC and slave cylinders only using the type of fluid I planned to use in the system, to clean and lubricate parts as I reassembled. One problem with this is that during a long-term restoration a rebuilt cylinder could get stuck, while awaiting the rest of the car to come back together. Also, I've torn or damaged a few seals, occasionally gotten a piston stuck, or similar. Never fun, but I always just accepted it as a part of the job. Just recently I was at my local auto parts store and found Raybestoes Hydraulic Cylinder Assembly Lubricant there. It's basically a medium weight oil that's compatible with all types of brake fluid and works better to lube the parts during reassembly, and can be sparingly coated on the inside of cylinders, caps, metal reservoirs, etc., to protect against corrosion while the system awaits the rest of the restoration. I'm trying it and just wanted to pass it along. Already I managed to free a stuck seal on a clutch master cylinder that was rebuilt a year ago, but hasn't gotten back on the road yet. I've got a couple calipers about to be fitted with new pistons and seals, will use it there too. We'll see how it works! The instructions emphasize this is not an additive to the fluid of the brake system and should be used very sparingly during assembly.