Quick answer

Choose the RUSAN MAR-FX adapter that matches your clip-on's objective lens thread diameter and your daytime optic's eyepiece diameter. The modular clamp design lets you mix and match sizes for a secure fit.

Why size matching matters

A mismatched adapter can cause misalignment, image degradation, or even damage to your optics. The MAR-FX system uses interchangeable clamping rings, so you can adapt to different objective diameters without buying a whole new mount.

Thread compatibility

The adapter connects to your clip-on via a threaded interface. Ensure the thread pitch and diameter on the MAR-FX match your device. If your clip-on uses an uncommon thread, check if an optional thread adapter is available.

Decision rules for choosing your MAR-FX adapter

  • 1. Measure your clip-on's objective thread: Check the thread diameter and pitch (e.g., M46x0.75) on your thermal or night vision device. The MAR-FX adapter must match this thread exactly. Write down the thread spec before ordering.
  • 2. Determine your daytime optic's eyepiece diameter: The adapter clamps around the eyepiece of your riflescope or spotting scope. Measure the outer diameter of the eyepiece to choose the correct clamping ring size. If your eyepiece diameter falls between two ring sizes, choose the larger one and use shims if needed.
  • 3. Verify repeatability requirement: The MAR-FX (Modular Adapter Repeatability) is designed for quick detach and reattach without losing zero. If you frequently swap your clip-on between rifles, this is a key advantage. For a one-time permanent mount, a simpler fixed adapter may suffice.

Product facts

Who should choose the MAR-FX

Best for

  • Hunters who need to quickly move a thermal or night vision clip-on between multiple rifles
  • Users with a clip-on that has a standard thread diameter and a daytime optic with a common eyepiece size

Not ideal for

  • Permanent installations where repeatability is not needed
  • Clip-ons with very uncommon thread pitches that lack a compatible thread adapter