Use: for violin bows:
++ : really cheap and very good for its price
+- Take care not to touch the hair of the bow with the plastic of the package. Not a big issue though.
- you get only a small quantity of the product; however you have enough for several months.
All and all use this instead of the rosin that comes with the violin (I bought a Stentor SR1500 Violin Student II): while you might not see the difference in the beginning, after some time you really must pass to something better, and Gewa Rosin Karwendel is a good product for its price.