Compression lugs and terminals are the workhorse connection components of stranded-conductor electrical wiring, used wherever a flexible cable needs to terminate at a bolted bus bar, a screw-terminal device, or another fixed connection point. The lug is a metal sleeve and connection tab combined into a single component — the sleeve receives the stripped end of the cable conductor, and the tab provides the bolt-hole or other connection feature that interfaces with the downstream device.
Installation is done with a calibrated crimping tool that compresses the lug sleeve around the cable conductor with enough force to deform the strands into a gas-tight metal-to-metal contact. Done correctly, the crimp creates an electrical connection that performs as well as — or better than — a soldered joint, with superior mechanical strength and no risk of cold-flow or thermal degradation over time. Done incorrectly (with the wrong die, undersized cable, or insufficient compression force), the crimp can be a high-resistance failure point that overheats under load.
The lug family includes several common configurations. Ring terminals have a closed-loop tab that captures the bolt — used where the bolt passes through the tab and is unlikely to be removed during normal service. Spade terminals have an open-loop tab that slides under the bolt head — used where service requires occasional disconnection without unscrewing the bolt completely. One-hole lugs have a single bolt-hole in the tab; two-hole lugs have two bolt-holes for higher-current connections that require redundant mounting and reduced contact resistance. Long-barrel lugs have an extended crimp sleeve for added contact area on very large conductors.
Material construction is typically C11000 electrolytic-tough-pitch copper (the highest-conductivity copper alloy widely available) with tin plating for corrosion resistance and improved long-term contact stability. The tin plating also makes the lug suitable for use with aluminum conductors when the appropriate antioxidant compound is applied. Lugs sized for cable from 14 AWG up through 1000 kcmil cover essentially all conductor sizes encountered in commercial and industrial electrical work.