A2028 - 20mm Back To Back Block – Our back to back blocks feature two sheaves, both with our patented dynamic bearing technology. The sheaves face opposite directions to allow two control lines to run at a maximum of 180 degrees to each other. Held together with a strong stainless steel side strap and nylon mouldings ensures the block will not separate even under two very high opposing loads. The strength of the design lends itself to be tied around the middle in the slight V shape, meaning it can be used in applications such as triangle backstay systems found on sports boats. One of the more popular applications is in a dual pole and spinnaker launcher system such as the system commonly found on a 49er.