U.S. Seal PS-961 Seal Assembly for SpasPS 961 U. S. Seal Shaft Seal Assembly The U. S. Seal PS 961 is Specifically suited for Spa and Hot Tub Applications. The PS 961 uses Sintered Carbon providing better resistance to heat, abrasion and chemicals. Description: 5 8" Shaft Premium Seal Designed for Spa and Hot Tub Applications Buna Carbon Graphite SS with Ceramic Seat Recommended for Hot Tub and Spa Applications Not Recommended in Pools or Spas with Ozonators, Bromine or Chlorine