Good quality synthetic lube. For example, it's "food safe" and the refrigerator uses a noisy plastic door that opens and closes to let cold air into the refrigerator compartment. Used for the gears of telescopes and other delicate instruments. Only deducted a star because of the price. I've also used the spray version of this lube, but this is obviously the best coverage as it doesn't need to be sprayed into a carrier that dilutes it. This grease gun tube is currently much less expensive than the smaller tubes per ounce but still expensive.