The nock sizes are not based on the string they should be used with. The different letters distinguish the sizes so that you know which shaft they will fit. They will typically have a tighter fit on traditional strings. The fit on the string will depend on how many strands you are using and what diameter of serving material. If you have any questions regarding which nocks should be used for which shaft, give us a call at 1-866-587-9501.
Answered on 6/16/2011 by Justin from 3Rivers Archery