Feature: 1. 4 Grooves: Optical flipper includes 4 grooves into which lenses can be inserted, humanized design, meet your use needs, but please note that this product does not include lenses. 2. Adjustable Interpupillary Distance: Professional and reasonable design, firm frame, pupil distance can be adjusted, easy to use, clear measurement, considerate and practical for use. 3. Vision Training: Optometry flip is suitable for vision training. It needs to be used with vision cards and lenses (not included). Generally, after 15 days of training, it can effectively improve vision. 4. Non Slip Handle: There are grooves on both sides of the handle, non slip design, easy to hold and operate, important and necessary eye health care tool. 5. ABS Material: Adjustable optical flipper is made of high quality ABS material, safe and eco friendly, firm and sturdy, stable and wear resistant, durable for use. Specification: Item Type: Optical Flipper Material: ABS Adjustable Range of Interpupillary Distance: 45-90mm / 1.8-3.5in Package List: 1 x Optical Flipper Note: This product does not contain lenses and does not contain vision cards.