Coma correctors, field flatteners and focal reducers require that the camera sensor be positioned at the perfect distance from these lenses.

The M68 Astroworx shims are used to precisely adjust this distance: each ring is made of stainless steel and can be inserted over each M68 male thread. They are also useful when the M68 threads are too long and need to be shorter.

Specifications:

• Inside Diameter: 68.1mm
• Outside Diameter: 76mm
• Available Ring Thickness: 0.2mm | 0.5mm | 1.0mm