I cannot recommend them enough! After speaking about Lascar expedition to severeal agencies, finding Retur was a relief. From the very beginning, they made us very comfortable by being honest and transparent about how the hike would look like and how they would manage any possible issues. They assured us the guide was very well prepared and would follow all safety measures that are in place in expeditions like this. Unfortunately, I was able to experience this personally, as my saturation dramatically dropped and I panicked. Great news though is the guide was 120% what they claimed, and he was fully capable of handling the situation with mastery! As a result, I didn't go all the way to the top (5600m asl) but I got to the crater (5500m asl) thanks to their amazing guidance, mountain experience and interpersonal skills. Other two people in my group experienced altitude sickness as well and again the guide managed it perfectly. Besides having a delicious breakfast with a view and the adventure of a lifetime (which you can probably find in most agencies), my greatest take from my tour is the absolute priority of having THE skilful guide I had with Retur, and this is why I trusty and recommend them so much.