Heat-resistant and UV-resistant silicone round rubber bands, 4.5cm diameter, 1mm thickness, set of 30. - Diameter: 4.5 cm - Thickness: 1 mm - Quantity: 30 pieces - Heat resistance: -50 to 200°C Thank you for viewing. Rubber bands naturally break over time, right? That's because rubber bands are made of natural materials and have low UV resistance and durability. These rubber bands are made of silicone rubber and have excellent weather resistance. Silicone rubber is also virtually unaffected by ozone. Furthermore, the physical properties of silicone rubber hardly change even when exposed to UV rays and wind and rain for long periods. They are also heat resistant, withstanding temperatures from -50°C to 200°C.