ThorLabs D37SZ - Zero Aperture Iris, Ø37.0 mm Max Aperture 

Aperturea: Ø0.0 mm - Ø37.0 mm (Ø0.00" - Ø1.46")

Size (Outer Diameter): 2.13" (54.0 mm)

Thickness:  0.30" (7.5 mm)

Black Spring Steel Leaves

Continuously Variable Iris Diaphragms

Dual Layer Leaf Design Reduces Aperture to Zero When Closed

This Items have No Mounting Holes