Flex-Drain 55020 Drain Pipe Coupler Adapter, Female to Female Female to female coupler for joining 2 cut pieces of FLEX-Drain Can also be used to adapt FLEX-Drain to some wyes and tees Exceeds all applicable ASTM standards Compatible with most traditional 3-inch and 4-inch corrugated pipe and 4-Inch PVC 30-Percent higher load-bearing rating than standard corrugated pipe