If memory serves me right the original ProPack does not have the threaded hole for the eye bolt that holds the ducer. The newer ProPack II has 3 holes for the eye bolt though. The Genz pack has one hole and the Ultra has 3 I think. The eye bolt threads directly into the plastic, there is about a 1/2" of plastic that is threaded. On my Genz pack the threaded part is about 3/4" but I have a nut on the front and back of the eye to keep it from rotating.