These are stalk mounted LED units mounted on frangible couplings (which break off if struck). They are red on the one side and green on the other with the green being at the appropriate angle for landing.
The body is an IP65 plastic enclosure, 90mm deep, 117mm high, 117mm wide (outside). Only the terminals of the LED's protrude into the box so there is space for transformer, lightning protection and termination. The units are supplied standard with red and green LED's wired in parallel to a 1.5mm square cabtyre which protrudes 300mm below the frangible coupling. The coupling needs should be bolted onto a solid surface eg. a 4mm plate bolted onto a manhole.