Holosun 507C X2 vs 507K X2: Size, Window and Footprint

Both use a CR1632 and Holosun rates each at 50,000 hours, but they are not drop-in swaps: the 507C X2 mounts on an RMR footprint, and the 507K X2 mounts on Holosun’s K footprint. Every figure below is copied from Holosun’s own product pages, checked November 4, 2026.

At a glance

• OpticHS507C-X2

  HS507C-X2
• OpticHS507K-X2

  HS507K-X2

Footprint and slide fit

Holosun’s 507C X2 page says “Direct Mount RMR Footprint” and “Industry standard RMR footprint allows direct mounting to a wide range of optics ready pistol slides.” The 507K X2 page says it is “Designed around the Holosun K footprint” with “Direct Mount K Footprint.” An RMR-cut slide takes the 507C; a Holosun K-cut (or MOS-K) slide takes the 507K. They are not the same cut.

Which to pick (on paper)

• If your slide is cut for RMR: the 507C X2. Holosun lists the larger 0.91″ × 0.63″ window and RMR footprint.
• If your slide is cut for Holosun K (micro-compacts): the 507K X2. Holosun lists 1 oz and the K footprint.
• If weight is the deciding number: the 507K X2 at 1 oz vs the 507C X2 at 1.5 oz (both Holosun body-weight figures).

We have not range-tested these; facts below are from the makers.

Related: 507C X3 vs X2, 407C X3 vs 507C X3, pistol red-dot footprint chart, new red dots 2026, 507COMP vs 507C X2, 407C X2 vs 507C X2, Holosun 507C X2 vs Trijicon RMR Type 2, 407K X2 vs 507K X2, all comparisons., 507K X2 vs EPS Carry

Frequently asked questions

Sources

1. Holosun: HS507C-X2 specifications
2. Holosun: HS507K-X2 specifications

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