Qingsi 2 Pack PD Ruler Optical Vernier Pupilary Ruler Distance Meter Eye Ophthalmic Tool Straight Edge PD Ruler

Material: PVC.Measurement Range: 0-100mm.The pd ruler can help you when you want to buy glasses online. Size: Approx. 21*5*0.7cm/8.26*1.96*0.27" (L*W*T). EASY TO USE: Put the notch over your nose, as close to your eyes as you can, then find the middle if your pupils in a mirror, read the line closest to the middle of the pupils. NO INSTRUCTION COME:  Does not come with any instructions, so if you don't know how to take a PD measurement, you will need to look that up on the internet. PACKAGE INCLUDE: 2 Pack Plastic Optical Vernier PD Ruler.