Disco Velocity Regulator?

[shadowr1]

I'm thinking about getting one for my disco and would like to know if one is better than another and are they worth it?
These are some I've found, I know TKO has one but I can't find a pic for it.
http://www.airgunsmith.com/benjamin_discovery/benjamin_discovery.htm
https://www.airgunsofarizona.com/CustomParts.htm
http://www.bigedmachining.com/crospart7.html

[shadowr1]

I thought about the just putting a screw in it but decided I would like something that looks better.