Foam peanut

They are roughly the size and shape of an unshelled peanut and commonly made of expanded polystyrene foam.

[1] Polystyrene-based packing peanuts were developed and patented by Tektronix Inc.[2] They were made commercially available circa 1965 by Dow Chemical.

Often green is 70% or possibly more recycled polystyrene, white is 70% or more virgin resin and pink means an antistatic agent has been applied; although there are some variations.

[3] Foam peanuts are very light (usually around 3 grams per litre/0.17 to 0.2 lb per cu ft) and easy to use.

Because of their build-up, polystyrene peanuts may also be used for various methods of home insulation, although it is not recommended because they are not flame retardant.