I have the older generation (about 3 years) of this. I have been very pleased with my dogs Ruffwear pack. Lexie has successfully packed into the high Uintah's three times with her pack. You definitely want to fit the under-harness well before you start your hike. If the under-harness is not fitted well, it can cause chaffing and raw spots. It is also important to make sure the load in each side of the pack is balanced or one side will sag uncomfortably. It has taken my dog a while to get used to carrying her own weight. However, I think letting Lexie carry her own gear makes her feel more like one of the pack (pun intended).