Sokkia B20 . B21 Product Description: The Sokkia B20/B21 offers the best of our famed leveling technology in a more compact, easy-to-use design. Tougher, smaller and mire tightly sealed against humidity and dust-for superior performance whatever the conditions. What is more, the B20/B21 is quick and easy to set up, simple to sight, and immune to vibration and shock.