Harken carbo 57mm boom block 5sh, its the perfect fit for a 1:10 system. Low-friction Carbo Air blocks are lightweight, strong, reliable—and affordable. Companions to the popular Harken Black Magic block line, these small, compact blocks. They have very high working loads for safe and easy trimming.
The 1:10 system is most used on the F16 and F18’s, NACRA 17 and the Nacra 20Carbon.