If you are like us, you have always used brake fluid as an assembly lube when rebuilding a brake caliper. It turns out that brake fluid is not ideal for this process, though. For one thing, it's quite aggressive against painted finishes, not to mention human skin. For another, it tends to get gummy when exposed to air and the moisture contained in the air.
A better solution is a dedicated assembly lube. This brake caliper assembly lube is nice and slick for easy pressing of pistons into caliper bores. It's gentle on painted surfaces, and it won't gum things up if it's exposed to moisture. Compatible with all brake fluids.
One bottle contains about an ounce of assembly lube, which is enough to assemble many calipers.