There are two different types of nocks for crossbows. Half moon and Flat. Parker suggest the half moon, which are suppost to stop the string from going over or under the arrow. Carbon is more forgiving then aluminum. They bend and go back striaght. Aluminum bends then are no good. Buy and use what you can afford. In the long run carbon many be cheaper.Parker needs anarrow, because of the anti-dryfire,to shoot after you get done hunting. That is about the only way to unload a crossbow.

Hope This helps. There are other forums out there that are just as good. Use Google.

Dave