Upgrade your Brompton bike with the 13 Tooth Rear Sprocket (3mm) designed for 3-speed and SRAM 6-speed systems. This silver sprocket ensures smooth gear transitions and optimal performance. Compatible with Brompton 3-speed BSR wheels and 3/6-speed SRAM/Sachs rear wheels, it's perfect for enhancing your bike's ride quality. Lightweight and durable, it's a reliable replacement or upgrade.