●▶【4 sizes per set】4 tubes of equal length (300mm) with a 1mm thickness. Different external diameters (+/-0.1mm): 5mm, 7mm, 9mm, and 11mm. The various sizes allow you to experiment and find the right material selections for your different DIY projects. ●▶【Ultra lightweight】100% carbon fiber. Exceptional strength and stiffness-to-weight ratio. ●▶【Built for maximum strength and durability】Resistance to corrosion and heat. Made of carbon fibers with 3K tow, roll wrapped, and weaved in 2x2 twill. ●▶【Versatile applications】Racing cars, boats, drones, robotics, telescoping poles, idler rollers, kite frames, and so on. ●▶【USA business】Developed and supported in the US, this product is guaranteed for free returns within 30 days of purchase. If issues with the product occur after 30 days, please contact us, and we will do our best to resolve your concerns.