The Holosun K-series footprint is a standardised pattern of screw holes and recoil bosses. Optics built to it include the Holosun 407K, 507K and EPS family — and any mount, plate or slide cut machined for the Holosun K-series pattern takes any of them, whatever the optic's brand.
Before ordering, confirm your mount, plate or slide cut is machined for the Holosun K-series pattern — the pattern decides the fit. Reticle, window size and dimensions for each sight are under Key specifications on the product page.