We commissioned laboratory evaluations of several available hollow glass microsphere products. Particle Technology Laboratories made particle size measurements for 3M™ K1 and Potters Sphericel™ 25P45 hollow glass microspheres (HGMs). The measurements were made in August 2020 at PTL's laboratory in Downers Grove, IL. The purpose of the measurements was to evaluate widely available hollow glass microsphere materials obtainable from multiple sources for effectiveness in reducing ice melt. A further purpose was to select materials for evaluation in field experiments and to compare size distributions. A further purpose was to determine the percentage of particles below 10 microns for evaluation for safety. A further purpose was to compare particle size measurements with reflectivity measurements.The measurements were made by laser diffraction using a Malvern Mastersizer 3000 (Particle Technology Laboratories, Downers Grove, IL). Particles were delivered with dry sample introduction due to the buoyancy of the particles in typical solvents used for particle size measurement. The lowest venturi setting was used to avoid damage and breakage to the microspheres during sample measurement. Optical microscopy of the samples after particle size measurement confirmed the integrity of the particles through the laser diffraction measurement.