Brake Paste (anti-seize grease).
This paste/grease is used to protect the exposed pistons, preventing corrosion forming. It can be used on the brake pins and on the back of the pads to stop them rattling.
This paste is designed to be used on brake systems and has temperature resistance to over 1000'C. Do not use as a grease if assembling new brake seals. Red rubber grease is needed in this application.
One Satchet is usually enough to do three calipers.