The C Vision string is made by Thomastik-Infeld for 5-string 4/4 violins. You can use it with the Vision Strings set by Thomastik which includes the 4 first violin strings (E-A-D-G).
This C string is in silver over synthetic core, with ball-end. It has a medium gauge.
If you are playing an extended range electric violins having a 6th string, you can also use the F Vision string.