Cast Iron - Coupler coupler for various 2-1/2 - 3 pumps: 2-1/2, 2-1/2 NFI, 2-1/2 BI, 2-1/2 AB, LD3, LD3 BI, LD3 AB, HD3, HD3 BI, HD3 AB. Product Details For Use With Various 2-1/2 - 3 Pumps