Embodiments include polymer polyol dispersions which include a polyol liquid phase and solid particle phase. Embodiments include methods of making the polymer polyol dispersions. The polymer polyol dispersions are essentially free of tin, have a solid content of between about 20 and 50 wt % based on the total weight of the polymer polyol dispersion, and have a viscosity at 20 C. of less than 9000 mPas. The solid particle phase has more than 90% by weight of particles in the solid particle phase having a particle diameter of less than 5 μm.