This NEOPERL 0.5 GPM PCA Spray Aerator has a vandal proof, junior male 13/16 in.-27 housing. The exterior rotating sleeve of the aerator can only be installed and removed with a key so it prevents tampering. This makes the aerator ideal for use in bathrooms in commercial and multi-family buildings. The pressure compensating design helps to maintain a constant and comfortable water flow regardless of pressure fluctuations.