Hi David, yes sir, this comes with (1) 17rd and (2) 21rd magazines.
Stay safe & have a great day!

The modular pistol has arrived with the advent of Sig’s optional X-Change kits. Removing the P320’s fire control group unlocks hundreds of combinations for your Sig pistol. The kit includes a complete slide, barrel, recoil spring assembly, grip module and 17rd and 21rd magazine. The slide is reflex optic compatible and the kits are not available for manual safety.
Brand Sig Sauer
Category Parts Kits
Series M18 X-Change Kit
Model P320
Caliber 9mm Luger
Firearm Fit Sig 320
Capacity 17rd or 10rd
Color Coyote Tan
Hand Right Hand

Hi David and welcome. Yes, Includes:
Complete Optics Ready Slide
3.9" 9mm Luger Barrel
Recoil Assembly
M18 Grip Module
(1) 17 Round Magazine
(2) 21 Round Magazines
Cheers and stay safe!