LockNLube Grease Gun Coupler locks onto Zerk fittings. Grease goes in, not on the machine. World's best-selling original locking grease coupler. Rated 10,000 PSI. Long-lasting rebuildable tool. is a Tools & Equipment option for everyday use, business supply needs, resale shelves, or household stocking. Review product size, pack count, and shipping details before checkout.