I have the following Inrad Tentec filters for sale: #762 600Hz for Orion, great replacement for stock 1000Hz filter - $50 #753 400Hz for Argonaut, Argosy, Paragon, Omni and Triton - $75 #760 250Hz for Orion, Argonaut, Argosy, Paragon, Omni and Triton - $75. Checks or Paypal okay. 73 es Merry Christmas Neal - k3nc