https://www.micrainstruments.com/product-page/r637
R637 | Micra Instruments
R637 - 7.0mm Optical Fine Cross-Hair Zone MarkerDiameter option: 2.50mm, 2.75mm, 3.0mm, 3.25mm, 3.50mm, 3.75mm, 4.0mm, 4.25mm, 4.5mm, 4.75mm, 5.0mm 5.25mm,...
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