3M™ Glass Bubbles K15 are hollow glass spheres with a typical density of 0.15 g/cc and isostatic crush strength of 300 psi. These spheres are designed for use in a variety of oil and gas applications including drill riser buoyancy modules, buoys and moorings. Our K15 bubbles produce strong, stable voids with low thermal conductivity, helping coatings achieve the necessary compressive strength.