NEW - Hex-Duty Oil Sight Glass by Esco. The world’s leader in sight glass technology introduces the Hex-Duty Sight Glass. Stronger and more durable, with double the pressure rating at 400 psi. The new hexagonal design allows for easier installation, draining and disassembly. Available in 1-ounce and 3-ounce bottle sizes, with either a ¼”, 3/8”, ½” or ¾” NPT.