Metallics JLW171PL Washer 10 Plain Finish Med Split L/W (Jar 100)

The JLW171PL is a #10 medium split lock washer, so it goes under the nut or screw head on #10 machine screws and bolts. If you are fastening 1/4-20 or 8-32 hardware, you need the matching size in that series instead, not this one.

Plain finish, meaning uncoated rather than zinc plated or stainless. That is fine for dry indoor work like panel builds, device mounting, and enclosure interiors, but for damp locations or outdoor runs pick a zinc plated or stainless split washer instead.

Each jar holds 100 of the #10 medium split lock washers. The jar pack is the whole buying unit, so for a panel shop or truck stock you are ordering in hundreds, not loose pieces.

A split lock washer like the JLW171PL is what keeps a #10 screw from backing out under vibration, which is why electricians use them on strut hardware, device mounting, ground lugs, and enclosure covers. It is a spring washer, not a bearing surface, so if you also need load spread over sheet metal or a slotted hole, add a flat washer under it.

No. The JLW171PL is a split ring that acts as a spring to hold tension on the fastener; a flat washer spreads clamp load across the material. They do different jobs, and swapping a split washer in where a flat washer was specified can let the screw dig into thin sheet metal. Where both matter, use a flat washer against the material and the split washer under the nut.