When evaluating Siloxane Emulsion, you must prioritize the active content percentage (typically ranging from 40% to 60%) as this determines the dilution ratio and performance. Check the pH value to ensure compatibility with your substrate; for instance, alkaline-stable emulsions are required for fresh concrete. Additionally, verify the particle size (measured in microns)—smaller particles offer deeper penetration into porous surfaces, providing superior long-term water repellency and breathability.