To maintain your pet’s health and well-being, regularly check your pet’s watering systems’ parts for replacement. This black replacement cap is designed specifically for use with the Replendish Waterer system, in sizes medium (2.5 gals.) and large (4 gals.). To ensure a proper fit, be sure to match your pet’s watering system with the appropriate product/item number for this replacement cap. The cap size measures 5 1/8″ x 5 1/8″ x 3 1/4″