Features. An Armstrong Fluid Technology 807436001K Coupler Kit connects motor and shaft components for efficient circulator operation. Includes Coupling Sleeve, Coupling Flange X 2. Common Equipment Types Circulators. Fits Popular Models 10501, 10501.25, H51, H52Compatibility. 10501, 10501.25, H51, H52.Specifications. Size 0.5 x 0.5. Key Spec Includes Flex, H Series. Length 1 in.. Width 1 in.. Height 1 in.