Planetarium Premium Six-Piece Color Filter Set, 2" Eyepiece Planetarium Color Filters Represent the Finest In Quality and Precision Straie-free substrates are polished parallel to 30 seconds to eliminate wedge errors 7 Layer Multicoatings with anti-reflection multicoatings 2" Diameter for 2" Eyepieces and 2" Diagonal formats Freedom from Ghost images, even when stacked. Striae-free substrates are polished parallel to 30 sec