These are genuine silicon flies. Developed here in 1986. I actually created the first ones by coating a new glass vial of florescent material that John Goddard had been given in the UK to experiment with. We were fishing the Waihi stream mouth at night and they were deadly on fish. Unfortunately they broke when hit on the back cast no matter how careful you were and the light went out! I coated what we had left in silicon from a tube of household bathroom silicon and they worked brilliant but were too labour intensive to make up in numbers.
Tim McCarthy at Sporting life sports shop came up with the idea of using a plastic bag to mass produce them. Nowadays they are common place around lake Taupo and different colours are used.