3M Glass Bubbles K20
K20 glass bubbles have a density of 0.2 g/cc and an isostatic crush strength of 500 psi. The general purpose K Series glass bubbles are the most economical 3M glass bubbles.

3M Glass Bubbles K37
K37 glass bubbles have a density of 0.37 g/cc and an isostatic crush strength of 3000 psi. The general purpose K Series glass bubbles are the most economical 3M glass bubbles.

3M Glass Bubbles S15
Because of their high strength-to-weight ratio and spherical shape, S15 glass bubbles are used by formulators to increase filler loading, lower viscosity, reduce shrinkage, reduce warping and increase buoyancy.