The GoatLink is simply the fastest route to improved wear and long-term shifting performance on wide-range 1x10 drivetrains using the Shimano Shadow+ Rear derailleurs. The GoatLink, made by Lindarets and Wolf Tooth, re-positions 10-speed Shimano Shadow+ Rear derailleurs to the optimal location when using the GC 40T and GC 42T cassette expanders. Compatibility:- Compatible Shimano Shadow+ 10-speed rear derailleurs (clutch type ONLY) have a Direct Mount link (including spacer, if so equipped) or B-pivot knuckle with a thickness of 7.9-8.1mm. Shimano changed to this sometime in 2013. Very early Shadow+ rear derailleurs have a thinner link and are not compatible. Here is how to take that measurement: - The GoatLink is optimized for use with Wolf Tooth's 40- and 42-tooth GCs and all sizes of Drop-Stop chainrings - but will work with any 11-40t or 11-42t 10-speed cassette. - Direct Mount-native frames and SRAM rear derailleurs are not supported. - You will NEVER need a longer b-screw with the GoatLink- Improvements with the GoatLink*- Chain wrap at 11t (effects cassette life): - 40t: Improved by 69%- 42t: Improved by 53%Free chain length at 11t (effects shifting precision):- 40t: Improved by 25%- 42t: Improved by 19%