EMI Ultra Light Pupil Gauge Black. These Flashlights from EMI are activated by depressing the tail-cap switch. The EMI Ultra-Light Penlight has circles with diameters from 2 to 9 mm for comparison when evaluating the dilation of a person's pupils. The EMI Ultra-Light Pupil Gauge Penlight comes with a pocket clip for secure carrying in your shirt pocket cargo pocket or holster. Specifications for EMI Ultra-Light Pupil Gauge Penlight: Manufacturer: EMI Flashlight Application: Work Hiking Color: Black Finish: Metallic Diameter: 0.5 in Length: 5 in Additional Features: Tail-cap switch Three striking colors Pocket Clip Quantity: 1 Battery Type: AAA Included Accessories: 2 x AAA Batteries Package Contents: EMI Ultra Light Pupil Gauge Penlight 215 EMI 215: Ultra Light Pupil Gauge Black