Smart Ruler Pro is the 1st set of Smart Tools collection. It integrated 6 simple and useful tools into this app. Here is the list. 1. Ruler - length 2. ProtractorⅠ(Touch) - angle 3. ProtractorⅡ(Plumb) - slope 4. ProtractorⅢ(Camera) - goniometer, clinometer 5. Surface level - sprit level 6. Thread pitch - screw, bolt, nut * Pro version added features: - No ads - Multi-Touch mode - Caliper mode - Ruler Extension - Architectural and Engineering Scales - Various Tilt units - Screen capture * Do you want more tools? Get [Smart Tools] package. For more information, watch YouTube and visit the blog. Thank you. * It is a one-time payment. The app price is charged only once. ** No internet support : You can open this app without any connection. After installation, open the app 1-2 times with your device connect to WI-FI or 3G/4G.