if 364 is total arrow weight...you need to first subtract all accesories...insert, nock, bh, veins, wrap, anything on there besides shaft. then use your computer calculator ( or google) to divide the new weight by 24.25. this will give you gpi, grains/inch.

So if it is 364-100 BH-9 nock-13 insert-18 blazers=224 shaft weight

224/24.25= 9.237 gpi. pretty average. but this is just an example, your weights could easily vary.