I should have known better than to have bought any heads that use little bitty screws to hold the blades in place.
First head lost a screw after hitting a Block target a few times and the blade was flopping around so I sent NAP an email and asked them for some help and advice...two weeks, no reply yet.
Second head lost a screw in flight (after I had checked all the screws) on the 3rd shot into a Block target. The blade flopped around and on impact broke off and broke the anodized aluminum head itself.
I have one left that I'll put in a display case since I'm sure they won't be on the market for very long maybe I'll have a collector's item some day.
Pure junk guys and girls so save your money.