This 2.5mm inner and 4mm outer diameter Teflon tube is generally used as the pathway passing 1.75mm filament from multicolor station to the main printer.
It is the same 2.5mm inner diameter used by Bambu Lab's AMS, Anycubic's ACE Pro and other brand's multicolor stations.
Accessories and DIY parts are consumables, they do wear out after a period of time depends on how frequently being used. They also require users with DIY skills to install which might causing damage if not handled properly. We can only provide limited warranty for accessories once it is being used. In case if you have any problem with our products, please read through our Returns & Refunds policy and contact us within 7 working days of receiving your order.