This is an OEM Sig P320 Legion 9mm 10rd Magazine. These magazines feature the aluminum Henning Group floor plate. These work in any full size or Carry P320 (they also fit but protrude from the bottom of the P320 Compact and SubCompact). The narrow floor plates fit flush in the P320 X5 or Legion grip module with magazine well / funnel.
Henning Group sells the floor plates alone for $20 each making these a great value.