Crittal Baco Greenhouse Glazing Rubber Seal - 4mm Expanded Cord - Sold Per Metre

It is made from a closed cell sponge material which does not absorb water so is suitable for making watertight seals on boat hatches, lockers, enclosures, and cabinets. As a soft compressible material, it is ideal for joining into O rings or making other custom sized gaskets.

eBay