0.5mm Thick, C-Mount Brass Spacer Ring

05mm brass spacer rings used in optics and photonics applications are available at Edmund Optics

Extension Tubes with C-Mount and SM1 Threading

Flat Brass Washer O Ring Solid Brass Oring Gasket Shim Copper Metal Meson Pad Spacer M2 M3 M4 M5 M6 M8 M10 M12 M14 M16 M18 M20 - AliExpress

M4x40mm Female To Female Nickel Plated Brass Hex Standoff Spacer

Astronomical Accessary, Astronomical Ring, Spacer 1mm M48, M48 Rings

SCHOTT BG38, 25.4mm Dia., 3mm Thick, Colored Glass Bandpass Filter

25mm Diameter, C-Mount Polarizer Holder

uxcell knurled Insert Nuts - 10Pcs 1/4-20 Female Thread Brass

Astronomical Accessary, Astronomical Ring, Spacer 1mm M48, M48 Rings

0.5mm Thick, C-Mount Brass Spacer Ring

Elliptical Mirror 22.23mm Minor Axis UV Enhanced Aluminum