Severn Trent Services, of Tampa, Fla., offers two new underdrain filters, the TETRA “U” Block and TETRA “LP” Block. Both have a proven design that provides superior distribution for both water and air, separately or concurrently. Both are also popular for their lightweight construction, easy assembly that ensures a tight fit, long maintenance-free life, easy adaptation into a new or old filter design application and low headloss. The “LP” Block has a lower and wider profile, maldistribution and additional flexibility.