Replace the Sig Sauer P238 magazine base plate with a rail adapter so you can attach the MantisX to your P238.  This adapter replaces the baseplate on the 7-round magazine with the pinky extension. (Not compatible with the 6-round flush mag)

Preferred if you don't have light-accommodating holster and want to train with holster draws, or if the firearm doesn't have a rail.

Part number:  MT-2031

Installation:
The MagRail replaces the factory finger rest. To remove the pinky rest on the P238 7-round magazine, you have to slide the rest off the top of the magazine (the top being the same side that you insert cartridges into when loading the magazine.)

There is a lip/catch on either side of the base of the pinky rest that catches on the bottom of the magazine. There are two tabs, one on each side, that wrap around the bottom of the floorplate to keep the finger rest from sliding up. Spread the finger rest out, side to side, until the two tabs clear the floorplate and slide the finger rest up toward the top of the magazine to remove from the magazine body.

Install the MagRail adapter by sliding the adapter down over the magazine from the top of the magazine body to the bottom. The retaining tab built into the MagRail adapter will snap into place, securing the adapter in the same way the factory finger rest is secured. Lastly, install the center insert into the MagRail body.