Akron Brass Akromatic [738] 2000 GPM Foam Tube. Akromatic 2000 Foam Tube. The Style 738 Foam Tube is designed to simply and quickly clip on the Style 5178 or 5170 Akromatic 2000 nozzles. This new foam tube will provide the capability to air-aspirate foam up to 6:1 expansion ratio with AFFF foam.