Alright, let me tell you about these roller trolleys - they're seriously heavy-duty and make moving stuff along strut channels so much easier. Each set comes with the 4-wheel trolley, M10 bolt, and these lifting eye nuts that are super handy. Installation is a breeze - literally just push them into place on your strut channel and you're good to go. They work with standard 1-5/8 inch wide strut channels and anything taller than that too. The best part? These babies can support up to 770 pounds! That's no joke. They're made from solid steel with this rust-resistant galvanized coating, so they're built to last even in tough conditions. The wheels roll super smooth and quiet - no annoying squeaking or sticking. The bolt is hidden in this fastening groove so it doesn't get in the way, and you can even use these trolleys upside down if your setup requires it. Perfect for industrial applications, workshops, or any project where you need to move heavy items along a track system. The silver finish looks professional and the whole thing just feels quality when you handle it. Seriously, if you're tired of struggling with janky rollers that stick or can't handle weight, these are totally worth it. They come in a 2-pack so you can set up multiple points or have spares on hand.