Spark Professional Loupes come in many models and working distances, with clip-on, headband, and attached headlight models available. Product ships with regular(R) working distance unless you send us a message with a size, custom distances can be made upon request as well. Distance in Millimeters. Loupes can be worn without prescription lenses if you are not strongly near or far-sighted,but if your prescription is over 200 or 2.25(positive or negative)it is strongly recommended that you use clip-on loupes,headband loupes, ask us for the half frames,or have prescription lenses put in to your frames for metal frames(sports frames need to require RX inserts,which we can provide). Specification: Anti-glare coating which reduces light reflection to 0.3%. Full clarity of vision across entire field of view, no blurring around the edges. Adjustable pupil distance and viewing angle.Clip on models have a durable construction that safely clips to any glasses or loupes frame. Included accessories: Instructions, grip flip, lens cover, screwdriver, cloth case. Lightweight loupes with Galilean lens arrangement, very light for the quality, weighing less than a small cell phone (~42g). Compound Optics, available in XS (200-300), S (280-380), R (360-460), L (440-540), XL(500-600) working distances. It is light plastic construction, Pupil distance adjusts with one simple knob. Field of View 100-110mm.