Designed to fit perfectly to 10-inch or 20-inch long Big Blue (BB) housings to replace 4.5-inch dia filter cartridges

The inner diameter of the wrench is 5-7/8 inches between the shortest points and 6-3/4 inches between the longest edges

Compatible with most of the Big Blue type water filter housings that accept 4.5-inch dia water filter cartridges

Durable, strong plastic material

Full circle design with 4 teeth for grip