This U-Cup Rod Seal fits inside the plastic end cap in the damper leg of your fork. It's what keeps the oil in the upper leg. Be sure to click on the product pictures, as the second picture is a diagram showing where this seal is used in the fork. Almost any Manitou fork with a similar damper in the upper leg is going to use this seal inside the upper tube end cap.

Please note that some Manitou forks may have a u-cup seal that is slightly thicker, but THIS U-CUP SEAL REPLACES THEM AS WELL.