This Seal is a PS-2131 Seal used Primarily in Hayward Power-Flo, Power-Flo LX, Power-Flo II and Aqua-Flo TMCP Bath Tub Style and the Aqua-Flo Flo-Master FMVP Vertically Mounted pump wet ends. It is about 1 1/4" Across the back of the Spring Seal part that goes onto the Impeller and the Ceramic & Rubber part that goes into the Volute or Wet End Back is 1 1/4". The Hole in both parts is about 5/8". The Spring Seal part goes onto the shaft of the Impeller and the Ceramic & Rubber part that goes into the Volute. The Hole in both parts is about 5/8". To Install you should put silicon sealant on the shaft of the Impeller and gently push it onto shaft after you have put a small amount of Silicon on the Impellor Shaft. Also the rubber part can use a light coat of silicon to slide it into place in the Volute or Wet End Body. If you need an impeller and/or silicon look in our store.