I’m a amateur player started the violin in mid 30, have been playing about 15 years. The last several years, I used to use bernardel (also very popular one) until now, which I found too dry for my bow hair, especially this time of the year (winter). I've read so many good reputations on Guillaume, a bit more expensive but still not too expensive. And rosin, if you buy one, you can use it for so many years and it pays. So I decided to give it a try. It came in nice aluminium container, I think also keeps the rosin from drying out?...not sure about it, but sure to protect the rosin. I applied several times, and I was amazed to see the big difference! It really helps the bow hair to catch the strings! And you don’t need to apply it every time you practice like Bernardel. In summer, with more humidity, I think I can mix it with Bernardel to make the right texture. It really helps you to make clearer sound and with better response. I would definitely recommend it. Thank you so much Guillaume. Please continue making the wonderful rosins.