It has a rubber cover for the 2-pin connector to keep the electrical connects dry and corrosion free. Note: If your OptiMate has the black SAE connector, you need the O1. CONNECTORS: M6 eyelet to TM.
Optimate / Accumate TM71 Weatherproof Eyelet Permanent Charger Lead
Optimate TM71 Weatherproof 12v Fused Eyelet Connection Lead
Optimate O31 Weatherproof Eyelet Lead (O1 Lead with Green Lithium Cap)
OptiMate O1 SAE71 Weatherproof Eyelet Lead x4 Pack
Optimate O1 Fused Eyelet Battery Lead M6 Weatherproof SAE Connection
Optimate O124 Weatherproof Charging SAE Lead With LED Battery Status/Monitor