The micrometer is widely used for measuring of industrial accessories, handicraft, pearls and jewels. It can measure inside, outside, depth and step size with two sets of and the probe. I believe that will be a good idea, if you could give your children a handmade necklace as birthday gift, which is made of pearls in oysters. The micrometer caliper will help you , it is a good partner of pearl drill. Features - Color: Blue - Material: Plastic fiber composites - Size: 17cm(Length) - Made of strong Plastic fiber composites, lightweight and durable - Two way measurement, internal and external - Linear capacitive measuring system - setting in any position - With easy to read large LCD display - Minimum scale to read is 0.1mm / 0.01 inch - An tool for a broad range of industrial and automotive applications Specifictions - Measuring Range: 0-100 mm / 0-4 inch - Resolution: 0.1 mm / 0.01 inch - Repeatability: 0.1 mm / 0.01 inch - Maximum Measuring Speed: 1.5 / sec or 60 inch / sec - Display: LCD screen - Power: One Battery (not included), LR44 / 1.5V or 3V - Total size: 235 x 77 x 15 mm / 9.25 "x 3.03" x 0.59 "(approx.) - LCD display size: 15 mm / 1.57 "x 0.59" (approx.) - Main Color: Black - Quantity: 1 - Size for manual measurement, there may be a 0 to 1 cm error, belongs to the normal phenomenon. - Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package list: 1 x 0-100mm 4inch LCD Digital Electronic Fiber Caliper Gauge Micrometer (Blue)