Slight misunderstanding. My Groove is .366. The custom molds cast a bullet with a heel of .370 and a tail of .357. They are supposed to be a thumb press into the cases but I had to make a special crimp die to crimp them tight enough so they don't fall out. I was pretty disappointed with the two molds.I have some hollow base .358 bullets that shoot better than the bullets out of these molds but I don't have a mold to cast more.