Any flag that has a built-in 'tear-away' flap that can increase it's effective surface area.
The most commonly used size of flag that is referred to as a floppy is a 4x4 Floppy. These flags measure 4 foot by 4 foot and have a second piece of material that is connected to one edge of the flag. Velcro tabs keep the floppy flap attached to the flag for storage or minimized use. When a larger surface area is required of the flag, the flap can easily be 'torn-away' by pulling on the velcro to release the flap of material. Instantly, a 4x4 surface area is doubled into a 4' by 8' surface area of light blocking ability.