The BWG sport strap is probably the best sports strap you ever will own.
Mike Stuffler wrote at WatchUSeek: 
"It is worthwhile to mention that the BWG rubber straps are the most comfortable rubber straps I ever encountered, they are very smooth and feel very light."

This silicone sport strap is carefully designed for leisure and sport.
We created bigger and smaller openings for an optimum of cooling and ventilation.
This design avoids sweating very efficiently even in extreme heat and humidity.
The openings are created as typical and iconic Bavarian lozenges, therefore they are also a bold design statement.
Available in different colours, matching or contrasting the dial colour of your BWG watch. They make every BWG watch an ideal sport watch. 
This sport strap was tested over one year in every aspect of wearing until it was released after a couple of design changes.
The BWG sport strap fits to every 20 mm lug width watch.
But of course we strictly recommend buying a BWG watch.
The BWG sport strap has an integrated quick release fixing for easy replacement and changing colours in a few seconds without tools.

Size: 16,5 to 23,5 cm.
 
Material: medical grade silicone.