for all standard trial frames made of thin acrylic - a rigid Fresnel prism creates less distortion and aberration than the press-on prism of a corresponding power the practitioner can more accurately determine the tolerance of the patient to a given press-on - 7 rings 2, 3, 4, 5, 6, 8, 10, Dptp
Product Weight of the packaged product: 0.18 kg