My friend from Bali give me David's contact before we arrive to Sumatra. David met us near our hotel and advice plan on the trip. I want to note the excellent knowledge of the island, which showed David. He adjusted our plan, we were able to catch the most interesting places of the island, and not spend half the journey to a senseless way. In my opinion, without a guide on Sumatra is very difficult to find transport - only local people will be able to agree to the car for the trip provided on time - this is very important! David organized everything for 2-3 hours. David knows the places that are really worth seeing. Many places of tourist guides is not really as interesting as they are described - David is a native islander knows what you need. We spent a delightful day of rafting on the river Tropical, who organized and attended by David. We visited Bukit Lawang National Park too - nice place. No matter what you want - trekking through the jungle, a romantic journey through uninhabited islands around Sumarty, hardcore extreme in the most dangerous rivers of Sumatra - David organizes it all. And David, cool guy btw :)