Equipment lens holder with thumbscrew (2) Single Slit Disk Multiple Slit Disk OS-8523 Slit Accessory Equipment The OS-8523 Slit Accessory includes the following: Single Slit Disk Multiple Slit Disk lens holder with thumbscrew(2) 22 Equipment The OS-8523 Slit Accessory includes the following: - Single Slit Disk - Multiple Slit Disk - lens holder with thumbscrew (2)