Stability requires a mill that can deliver consistent shear without overheating. Key specifications include adjustable rotor-stator gap, sufficient motor power to maintain target throughput at stable particle size, robust seals compatible with hot asphalt, and a design that supports repeatable droplet size distribution. Materials should resist abrasion and corrosion from acidic water phases in cationic systems. Practical requirements also include reliable flow metering into the mill, temperature control of both phases, and easy cleaning access, because contamination and build-up cause instability and off-spec sieve results.