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ZWO’s 16.5 mm M48 spacer is a aluminum extension ring designed to reach optical spacing in imaging systems that require a precise backfocus.
It features M48×0.75 threading on both ends—male on one side and female on the other—making it compatible with a wide range of ZWO and other brand accessories, reducers, flatteners, and correctors.
This spacer is commonly paired with ZWO cameras that have a 17.5 mm native backfocus and their M54-to-M48 21 mm adapter. Combined, these components reach the standard 55 mm spacing needed for many optical setups (17.5 mm + 21 mm + 16.5 mm). It can also function as a short 2" nosepiece thanks to its M48 threads.
Machined from aluminum and finished with a black anodized coating for durability.
Specifications
• Male thread: M48×0.75 (4 mm length)
• Female thread: M48×0.75 (8 mm length)
• Total length: 20.5 mm
• Optical length: 16.5 mm
• Clear aperture: 43.2 mm
• Outer diameter: 50.7 mm
• Weight: 0.7 oz