Sorry i forgot that i was using a litter arrow then the ones that i sighted my pins in with but there is still about a 65 Grain diffrence (the ones i sighted my pins with are still heavier) but maybe they catch enough wind in flight that it makes up for them being lighter than the ones i sighted my bow in with. I dont know, all i know is that mine is sighted in perfectly. and to answer your first question, i think you have to buy them at a sporting goods store. Mine cost me 7 dollars for six