I use KMP reract that came with KMP P-47(old Version).
Although it is usable, it does not hold air pressure as long time as
other brands like Spring Air, CJM or Robart.
I suspect either the control valve or the retract cylinder lacks good
quality,precision or durability.
I want KMP sell them of two types,with retracts and without retracts.

Tsutomu Mabuchi