Maximum support high density knee sleeves
Neoprene knee sleeves do two things. They keep the joint warm, and they add light compression that makes the bottom of a squat feel more stable. They are support, not protection, and they will not fix a knee that already hurts.
Reyllen sleeves sit above and below the joint so they stay in place through repeated squatting rather than rolling down mid set. Neoprene holds warmth through a session and returns to shape between them.
Wear them for squat work, heavy pressing out of the front rack, and metcons with repeated wall balls, thrusters or box jumps. Take them off between pieces rather than leaving the leg compressed for a whole session.
Measure around the leg just above the kneecap and size from there. A sleeve should take effort to pull on. If it slides on easily it is too big.