These coasters include four designs from windows and a skylight designed by Frank Lloyd Wright. Two are from art glass details from Frank Lloyd Wright's Home and Studio in Oak Park, IL (1889). One is an art glass detail from the Isadore Heller House in Chicago, IL (1896) and the other is from the dining room skylight in the Ward W. Willits House in Highland Park, IL (1901). Each are made of porous sandstone and have a protective cork base. They are approximately 4 1/4" square and made in the USA.