An M20 bolt is 20.00 mm (0.787") in diameter. The nearest stocked ID is 3/4" (19.05 mm), which stretches on for a snug fit; 7/8" (22.23 mm) gives a clearance fit. All sizes ship in seven rubber materials.
Best in-stock matches for M20
| Washer size | Fit |
|---|---|
| 1-1/2" OD × 3/4" ID × 1/8" | Snug, compact |
| 2" OD × 3/4" ID × 1/8" | Snug, wider face |
| 2-1/2" OD × 3/4" ID × 3/16" | Heavy compression |
| 3" OD × 3/4" ID × 3/16" | Maximum coverage |
Browse all 3/4" ID and 7/8" ID rubber washers.
Sizing note
The 0.95 mm interference on a 3/4" ID means a firm stretch onto an M20 shank — excellent grip for sealing, but choose 7/8" ID if the washer must be repositioned or slid along the bolt. At this scale, 3/16"–3/8" thicknesses handle equipment mounting and vibration isolation best.
More metric bolts: M4 · M5 · M6 · M8 · M10 · M12 · M16 — or see the metric conversion guide, Size Finder and size chart.
FAQ
What size rubber washer fits an M20 bolt?
A 3/4" (19.05 mm) ID rubber washer stretches onto a 20 mm M20 bolt for a snug fit; a 7/8" (22.23 mm) ID slides on freely.
What are M20 rubber washers used for?
Equipment feet, tank fittings, dock and marine hardware, structural pass-throughs and large drain assemblies — anywhere a big fastener needs sealing or isolation.