Fangrui Product Details Improves Bike Efficiency Bicycle Rear Derailleur Hanger Precision Engineering Speed Change Extension Seamless Integration Description: Brand: Enlee (authorization Available) Product Name: Tail Hook Extender Material: Aluminum Alloy Weight: About 18g/set Application: 34-52t Flywheel High-strength Aluminum Alloy Material, Cnc Hollowed Out And Lengthened Design, Lightweight And Beautiful Specifications: Installation Method The Hook Extension Will Be Screwed To The Previous Frame Tail Hook, After Re-use, Pull Out And Install It On The Tail Hook Extension Seat. High Compatibility, After The Extension Of The Tail Hook Is Installed, The Space Between The Rear Pull Guide Wheel And The Large Tooth Is Sufficient For Speed Change. Mountain 40/42/46//5052t Etc. Highway 34/36/40/42t And Other Flywheels. Package Included: 1 Extender