The Fifth Wheel Lube Disks with Retention Clip from Buyers Products work to protect your trailer against wear caused by friction between the hitch and trailer. The disk slips over the king pin to provide constant lubrication, eliminating the need for fifth wheel plate grease and the constant cleaning and mess that goes along with it. Its large surface area provides extra towing protection by preventing wear to the hitch. The disks are available in three sizes, sold in boxes of five, and include the steel retention clip.