Any experience with Tier 1 Mag Holster Extension? +2, +4, +6

Looking at the Tier 1 Axis Slim in particular for the P365. I want to carry an extra 15 round magazine with me. Should I get the +2, +4, or +6 mag extender holster? Thanks. via /r/CCW https://ift.tt/2tLZeQh