3M 2228 Scotch Moisture Sealing Electrical …
It's far thicker than normal black electrical tape, and feels almost like a cross between tape and putty (it's that thick). It goes on flexibly, and later dries fairly hard (no reuse). It's fantastic for waterproofing outside junctions, as between sockets and bulbs where rain might get in.
DA: 26 PA: 88 MOZ Rank: 71