The bosch gol 20 d professional optical level is robust reliable and ideal for outdoor use due to its robust housing with dust and splash protection ip54 it is perfect for daily and prolonged use it offers fast aperture for excellent staff reading and a target collimator for rough alignment the compensator lock makes for safe transport and the penta prism makes it incredibly easy for the user to read the red circular vial it boasts erect image and a large focusing knob for easy alignment