This is the first purge on/off ASA I have owned, I have used other on/off ASA without purge and it is an extra step to shoot the pressure the out of your marker, on use tools to turn off the ASA because of the tank pressure.
I'm a hardcore poor gun whore, eleven (11) markers and counting:
WDP Angel LED 1999
3 WGP Autocockers (2 E-Cockers)
3 AGD AutoMags
2 JT E-Excellerators
1 VL E-marker
Easy to turn on and off with purge (as it is named), Colors
Expensive (listed at $40)
As I mentioned, this is the first purge on/off ASA I have owned I have used other on/off ASA without purge.
It is an extra step to get the pressure the out of your marker, or use tools to turn off the ASA because of the tank pressure. Usually I shoot out the pressure after the ASA is turned off, but sometimes you can't shoot the marker for one reason or another, that's where the purge ability comes in handy.
The purge allows the pressure in the marker's system to release, therefore removing your air source is easier and safer, it won't "pop" out and potentially damage the o-ring.
I managed to strip the set screw that locks the ball bearing in place, so it looks like it's stock on my DM4...
If you can find this, it's a great product, it's listed as retailing for $40 but I found mine on PbNation.com for $25 USD shipped USPS!!!