It is design to help you with catch angle and height in the catch.
 
Silicon part glow in the dark so it can be used during early morning and night sessions. 

In the package

1 units so it can be used for one rower per pair.

Best to use

Infront of the Central line of the boat. 

Installation

On the side edge of the boat.

After purchase:

You will get all of the Gearing tables and all detailed explanations.