Any base (no-ester) Anabolic Androgenic Steroids (AAS) can be used in a transdermal. The only drawback is, you really don't know how much is being absorbed. I've seen ranges from 10-40%, hence, it's the main reason why they aren't more popular. Your friend has found a method where he appears to be getting an adequate dose for his needs but who knows how much actual hormone is getting through.