

Monocular:
https://www.alibaba.com/product-detail/Hot-Sellers-MV265-7X-Lens-9mm_1601288508520.html?spm=a2747.product_manager.0.0.4e5471d2I1xyNH
Lens:
https://www.amazon.com/gp/product/B01F9KXRX2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
It is intentionally a tight fit. You will need to use a heat gun or a hair dryer to insert the lens and press the ring onto the optic. Once it cools it shouldn't move, or at least mine hasn't yet even after dropping it on the ground.
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