This material is a non-toxic, dense, small grain material you can use for those really small pockets where you need HEAVY ballast (you know, that little pocket in the airplane model NOSE/TAIL that nothing can fit in, etc.-?). LEAD (pellets, shavings, chunks) are NOT the healthiest to be fooling with, and you can't grind it THIS small (not safely, anyway)...just pour this in, and glue-Done.

while not actually a liquid, (very small pellets actually) the stuff acts like a liquid when filling in small spaces. does a good job to add weight, but be sure to saturate it with glue.

This is a bottle of very tiny metal balls. I used white glue to hold the balls in place than flooded the area with 50/50 glue and water to seal.