Those are Sho-Me bowfishing points and you have to use the tournament knot to attach your arrow to your line in order to get them off - they don't unscrew.
If you're looking for a head with a
lot of holding power/area that unscrews, I would take a look at Innerloc's new Grapple heads. I tried some of the 3 bladed ones the other day and they worked great. They're BIG but they fly great and cut through the water well too. Another feature I didn't know they had until I got them was that the replaceable tip has a rubber bushing inside of it to keep the tip from vibrating loose. Every time I shot my Muzzy QR or the Sting-O-Ree, I had to check and usually re-tighten the tip. Never had to do it once on the Innerlocs.
http://www.innerloc.com/Pages/prod_H2O.htm
Sully is selling them too:
http://www.sullysbowfishing.com/main.asp?Dept=Shop&Category=Rests