These double idler set ups are very strong and durable. The idler system is a key component in managing a long chain line on recumbent bikes and trikes. We like setting up the MetaBikes idler set up so it can float side to side with the chain on a 8mm bolt as you shift. This idler can be used for most recumbent bikes and trikes. 8mm is the most common bearing size opening. The price includes shipping.