GMO - Glass-molded (aspheric) Optics, less expensive than ground and polished aspheric. Glass molding employs high-precision aspherical molds, which are pressed directly onto glass to shape it into lens elements. Based on studies of glass materials and mold materials, Canon conducted simulations to create molds that ensure consistent and accurate performance even at high temperatures. Glass-molded lenses have found wide application due to the flexibility of their refractive index and other optical parameters.