Before You Measure
How to Find Your Outside Diameter (OD)
Don’t have calipers? No problem — here’s how to get an accurate measurement either way.
- With calipers (most accurate) — Open a pair of digital or vernier calipers, close the jaws gently around the tube or suppressor body at its widest point, and read the measurement in mm.
- With string or tape (no calipers needed) — Wrap a piece of string, a shoelace, or a soft tape measure snugly around the widest point. Mark where it overlaps, lay it flat against a ruler to get the length in mm, then divide by 3.14 (π) to get the diameter.
- Measure the right spot — For scopes, measure the main tube body, not the narrower eyepiece or the turret housing. For suppressors, measure the main body, avoiding any flared threads or mounts at either end.
- Between two sizes? — Round up for an easier, more forgiving fit. Still unsure? WhatsApp us your measurement or your scope/suppressor’s make and model and we’ll confirm the right size.
FIELDGUARD Suppressor Cover
Sizing Guide- Measure — Measure the outside diameter (OD) of your suppressor at its widest point, in mm.
- Match — 42–45 mm → Size 148–50 mm → Size 2
- Unsure? — WhatsApp us your suppressor make/model and we'll confirm the right size.
FIELDGUARD Scope / Optics Cover
Sizing Guide- Measure — Measure the outside diameter (OD) of your scope or optic tube at its widest point, in mm.
- Match — 38–45 mm → Small46–56 mm → Medium57–70 mm → Large
- Own more than one scope? — Save with a Small + Medium or Small + Large bundle.
- Unsure? — WhatsApp us your scope make/model and we'll confirm the right size.
In general, Small fits most eyepieces, Medium fits most 40mm objective lenses, and Large fits 50mm and 56mm objective lenses.
Minimum clearance required: a gap of 1.5 mm between the objective lens and the barrel.