The main difference is that the 510-4 is a soft neoprene sleeve, not a hinged, strapped or rigid brace. It has no rigid parts, so it does not block the knee from bending and is not designed to hold the joint in a fixed position. Instead, its effect comes from two physical factors: gentle elastic pressure and warmth. The mild compression keeps the sleeve close to the knee, which can make movement feel more stable and controlled; the neoprene retains heat, which helps keep the joint area warm during activity.
This makes the sleeve most suitable for situations where the knee feels strained under load, when you are getting back into movement after a break, or when you want more confidence during training, cycling, fitness or longer walks. A rigid brace is a different category and is normally chosen when a medical professional has specifically recommended restricting or controlling joint motion.
If you already have a rigid brace, this sleeve is not a replacement for it. And if your knee is unstable, swollen or painful enough that you cannot trust it during normal movement, do not rely on this sleeve alone; get professional advice first. As the product description notes, this support provides mechanical support only and does not replace medical assessment or treatment.