Astrozap Flexi-Heat Dew Shield for 5" SE AZ-818 Fits 149mm dia. Optical tubes One notch for side bar The Astrozap Flexible Heated Dew Shield uniquely combines both active and passive methods of dew fighting with the added feature of shielding the telescope from undesirable stray light. Felt-lined to help absorb moisture and to prevent extraneous light from reaching the optics and greatly improving contrast. Proudly manufactured in the USA!