I wouldn't give you a nickle for ultimate steel heads. The blade retention is extremely fragile and the little tabs that fit under the washer break very easily.

Yes they are sharp and made of steel but if it won't keep blades in the furrel on hard bone hits then what good are they?

The ST's are miles ahead of the US's. If you want a vewry small head that flys great use the NAP nitrons. About the same size as the US but a much beter head.