Drain & Return 1" & 3/4" Slip/Barbed Combo. Our custom one piece design is for easy and safe installation. For aquariums and filtration sumps. Manufactured with precision. (1) 1" Slip (pipe size) x 1.25" Barbed (hose/tubing size) Bulkhead (Requires 1" 3/4" Hole Diameter) + (1) 3/4" Slip x Barbed Bulkhead (Requires 1" 1/2" Hole Diameter). installations are easier and safer with barbed design. This is not a insert, its a one piece barbed design to avoid leakage.