Armory Craft Sig P239 PLUS-1 Base Pad.
 
TWO versions are available:
for 9mm magazines
for 40 s&w and .357 SIG magazines
 
- This base pad will increase the capacity by 1 round.
- Perfectly fitting base pads made out of solid aluminum billet and finished in durable hard anodizing. 
- Significantly improved grip ergonomics (Please see image #2)