what is the patch on the back of rugby shirts

The patch on the back of rugby shirts is a GPS tracking device. This device is part of a sophisticated biometric tracking system used by coaches to track a variety of data, including distance covered, speed, and heart rate, among other things. The data provided by the GPS tracking device can help both professional and amateur rugby players improve their performance. The patch is sometimes referred to as a "lump" or "bump". It is kept in place between the shoulder blades in something called a "Bro," which works in much the same way as a female athletes sports bra. The patch is not just a functional device, but it can also be a design element of the shirt. For example, some rugby shirts feature a flag-print twill patch on the back.