10 lb of Akulon K224-PG6 plastic injection mold pellets Polyamide Nylon Black.

 30% glass reinforced.

the pellets measure about 3 x 3 x 2 mm

275 C - melting point
They sink in water.
Can be used for weighted blankets, dolls
Rock tumbling
As sand replacement in koi ponds and aquarium filters.
10 fl. oz cup of them weighs 8 oz
22 lbs make about 1/2 cub ft.