Be careful using different companies inserts with different bolts, Even if everything was bang on a you achieve the required tension on your pull test, if anything ever went tits up and goes back to manufacturer, first question they'd ask is did you use our inserts/plugs with our bolts. Believe it or not, all of the nylon plugs are not the same, i know there's not going to be a massive difference, but would you really want to take the risk?? Good way for the suppliers to retain clientele once you've bought a shed load of bolts, agreed. If your supplier is any good though, they will advise you on the best product for the material your fixing to, i.e length of plug or length of bolt, with out wanting to just make an extra sale every time.