Hey, if you're dealing with sticky or noisy sliding doors or windows, these stainless steel roller pulleys are about to become your new best friends! This set comes with 4 double-wheel pulleys that measure about 12mm in diameter with a 16mm thick base - perfect for most standard sliding setups. They're made from solid stainless steel, so rust and corrosion aren't gonna be a problem, which is awesome for bathrooms, kitchens, or anywhere that gets humid. What I really love is how smooth and quiet they are - no more of that grinding noise or sticking that makes you want to rip the door off its tracks. Installation is straightforward with the 4.4mm mounting holes and 53mm spacing between them. They work great for sliding doors, windows, cabinets - pretty much anything that needs to slide smoothly. Each pulley has two wheels, which means better weight distribution and longer life. At 4 pieces in a pack, you've got enough for multiple doors or some spares for future projects. Seriously, if your sliding doors are driving you crazy, these little guys will fix that problem in no time!