dog, the insert you are talking about is a spacer i believe. it is for, if you do not use the timbersled drop brackets. but for the nytro, the drop brackets are required. so you dont use that spacer. the kit is the same kit basicly for the apex and the nytro. hence the double directions. the idlers tap on to the timber sled shaft (you might have to use the BFH as it can be a pain). ski