Grommets and bushings look similar and both live in holes, so the terms get used interchangeably. They shouldn't be — choosing the wrong one leads to chafed wires, vibration transfer, or a part that falls out. Here's the difference in plain terms.
What a Grommet Does
A rubber grommet lines the edge of a hole to protect whatever passes through it. The classic job: a wire bundle passing through drilled sheet metal. The raw hole edge would slice insulation over time; the grommet's groove snaps into the panel and surrounds the wire in soft rubber. Grommets also seal against dust and moisture and damp vibration between the panel and the pass-through.
Key trait: a grommet has a groove that captures the panel. It is measured by groove diameter (hole size), groove width (panel thickness), and inside diameter — our grommet size chart walks through all of it.
What a Bushing Does
A bushing is a sleeve that reduces a hole's diameter or bears load between two parts. Bushings support rotating shafts, absorb suspension movement, or adapt a large hole to a smaller fastener. They are usually cylindrical, often thicker-walled than grommets, and may be rubber, bronze, nylon, or rubber bonded to metal.
Key trait: a bushing is measured OD x ID x length, has no panel groove, and is typically press-fit or captive between components.
If what you actually need is to isolate a vibrating part from its mount, neither is ideal: use rubber vibration isolator mounts. For a big pass-through, the 2" ID rubber grommet (fits 2-1/4" holes) is a common size, and a rubber O-ring is the part to use when the seal sits in a groove on a shaft or fitting.
Quick Decision Guide
| Your situation | Use |
|---|---|
| Wire, cable, or hose passing through sheet metal | Grommet — shop rubber grommets |
| Sealing an empty hole completely | Blank grommet or plug — closed grommets / rubber plugs |
| Spacing or cushioning between a bolt and a hole | Rubber washer/spacer — neoprene washers |
| Supporting a rotating shaft or absorbing pivot movement | Bushing (application-specific) |
| Isolating equipment vibration from a panel | Grommet or bumper mount — compressor grommets |
The Gray Area
Some parts genuinely do both jobs — a thick-walled grommet cushioning a bolt acts like a bushing, and rubber-lined P-clamps blur the line further. When in doubt, ask what the part must survive: edge protection and sealing points to a grommet; load bearing and alignment points to a bushing. Material matters too — for oil-exposed automotive spots choose Buna-N, for outdoor UV exposure choose EPDM (full breakdown in our rubber material guide).
FAQ
Can I use a grommet instead of a bushing?
Only for light duty. A grommet cushions a wire, hose or cable passing through a panel, but it is not made to carry load or support a moving shaft. Where a part bears weight, rotates or needs a hole reduced to a smaller fastener, use a bushing.
How do I size a rubber grommet?
Match three numbers: the groove diameter to your hole, the groove width to your panel thickness, and the inside diameter to what passes through. The grommet size chart lists every size we stock.
How is a rubber bushing measured?
A bushing is measured outside diameter x inside diameter x length. It has no panel groove. Our rubber bushings list the stem and center-hole sizes for each.
What grommet goes in an electrical box knockout?
Use the knockout hole size, not the conduit trade size: a 1/2" knockout is a 7/8" hole. The knockout grommet size chart matches each trade size to a grommet.
