Over in Europe, Booby flies have foam eyes in the front of the fly. They look similar to larger dumbbell eyes. The are commonly used on still water, often with a sinking line and long leader to give the flat movement and life.
The also also very common on buzzer (midget emergers), where the foam is used as a post off the top / front of the fly.
State side, these are more commonly used for post one emergers, mostly parachute emergers. The are also great for a floating nymph pattern, used like they would be for a buzzer.
*Size 3mm was formally 2.6mm
Single colors are 20 pieces per pack. The mixed color pack has a total of 80 pieces in a nice storage box.