What are these tubes called, where can I buy them
There isn't a name for them. You need to find tubing the right size and tap the ends. If you're lucky (or thoughtful) you'll find tubes whose ID is exactly the tap drill size of the bolts you're using.
@gbj_tester started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
There isn't a name for them. You need to find tubing the right size and tap the ends. If you're lucky (or thoughtful) you'll find tubes whose ID is exactly the tap drill size of the bolts you're using.