Knee Guard ReaFlex UltraLite

These pads are unmatched for trail-riding comfort, with the thin mesh sleeve having enough compression to prevent slippage, while not being so tight that the seams dig into your skin.

Source: https://www.bikeradar.com/advice/buyers-guides/best-mtb-knee-pads

Size down they were a bit big

(Editorial Recommendation) Maximum comfort and a perfect fit: that's what the perfect knee pads should be like. The Leatt AirFlex UltraLite pads meet these requirements perfectly and fit like a second skin. They don't get in the way even during long rides, so you don't have to keep taking them on and off.

Source: https://www.bike-x.de/mtb/tests/mountainbike-outfit-fuer-den-sommer-damen-herren-v1/?utm_source=newsletter&utm_campaign=mountainbike-newsletter&utm_content=artikel-teaser

Leatt’s Reaflex range is a prime example of the brand’s goal. The pads are light enough that they can overcome objections to wearing pads while also providing CE-level certification
https://cyclingmagazine.ca/mtb/leatt-airflex/

The Reaflex Ultra Lite is a superb blend of super-lightweight materials and CE-certified impact protection. Engineered to help achieve maximum pedal efficiency, the longer leg sock provides support to the thigh region whilst alleviating pressure on the calf. Constructed from premium mesh to provide ventilation, the impact gel pad on the Ultra Lite fits neatly into a mesh pocket to hold it in place, with an abrasion-resistant patch over the knee. https://theloamwolf.com/2023/02/09/leatt-releases-two-new-airflex-knee-guards/