Shimano Tiagra RD-4700 10 speed rear derailleur Cable Adjusting Bolt Unit.

The following are an "A" match which indicates that the parts are the same in materials, appearance, finish & size etc.

- Shimano 105 RD-5800-SS/GS
- Shimano Metrea RD-U5000-SS

In a pinch, broadly compatible with rear derailleurs with a M5 barrel adjuster!