Upgraded replacement cylinder cap for blade tension cylinder on Marvel models 81 and 81A, series 7 through 12. This replacement cap has a double groove at the ID to reduce leakage at the rod. The OEM caps will leak if cylinder nuts are tightened to the top and bottom of the column, use a jam nut or set screw nut to leave a small gap, which will allow the cylinder to float properly. Alternate part number 81DBCC55D2.