The ALTRA Aluminum Topspin from BULLS are shafts which consist of aluminum and a top spin cup. These shafts ensure that your flight can rotate 360°! These shafts are available in 2 sizes: SHORT: 37mm, 1.74g & MEDIUM: 47mm, 2.05g. You can easily replace shafts with any dart. They are available in different sizes to customize your dart in length and feel. Sizes: XX-Short/Micro, X-Short, Short, In Between, Medium & Long. In addition, they also consist of different materials: nylon, carbon, plastic, metal, etc. In short, you can adjust your dart to your own taste and feeling through different types of shafts.