When it comes to building today's high-precision kits, a pair of calipers are a must. Ruddog Products' Digital Calipers have a measuring range from 0 mm to 150 mm and come in a handy plastic storage box to protect it against damage when not in use.
 
Specifications:
Resolution
0.01mm/0.0005" 
Power / Battery
One Button Cell (3.0V CR2032)
Accuracy
±0.02mm/0.001"(<70mm) 
±0.03mm/0.001" (>70-200mm)
±0.04mm/0.0015" (>200-300mm)  
Repeatability
±0.01mm/0.0005"