The Cose Rectangular Buckle with Slider, 30mm in red, is a rectangular frame-shaped plastic buckle used to adjust the length of straps and belts without a fastening function, only a sliding mechanism. The red color makes the piece stand out, making it a popular choice for backpacks and accessories with a more vibrant style. It is an essential accessory for those who make backpacks, bags, and adjustable straps in handcrafted leather goods.