This mounting standard is generally found on compact NV and thermal clip-ons. Infiray was the first company to use it. Most of these are supplied with converters (M30x1.0 to M52x0.75) which is probably one of the reasons why there are not as many adapters available in this category. All the clip-ons that feature this mounting standard are front-mounted, meaning that they are mounted on the riflescope’s objective.
Infiray CTP13 mounting standard (M30x1.0) on Infiray CLM25
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Our article with all the mounting standards on NV and thermal clip-on devices is available here