Three sided Internal Overflow is 6"x 10", has a 1" Silent Drain Pipe Assembly and a 1/2" Return assembly with T swivle discharge flare. Used for tanks up to 24" tall. This overflow is incorporated into the middle of the back or end of your tank ( PLEASE TELL ME WHERE ). It is used along with a Wet-Dry Trickle filter. The overflow has a Silent Stand Pipe ( similar to a Durso ) assembly, which raises the water level in the overflow and provides silent draing of the overflow. This provides no pre- filtration.  Additionally, this internal overflow includes a Return Assembly, this is used to mask the hose that brings the water from the filter pump below back into the tank. It comes with a barbed fitting below the tank and a swivle discharge nossle that is 2 inches below the water level.
The overflow is black by default unless YOU specify otherwise. All bulkheads are included and all bulkhead holes are pre-drilled. See Internal Overflow in out Library Section for more information.