Just thought I'd add to this, a couple of months ago the 007p was replaced by the 008. The differences are,
*The top does NOT turn to adjust it has 3 allen cap screws to remove the top.
*Then you change the spring as per the 007P.
*The flow is very similar to the 007p, but the vacuum chamber has been made smaller which causes the piston to react quicker than the 007p.
*Also the piston design is different and now has seals on the piston body to make an even beter seal
and as a bonus you get a free forge keyring and all the bits needed to take it apart and clean it etc, plus all the different springs and spacers