Kong Lin is very friendly and helpful. We had a terrible experience with the apartment we pre-booked. We decided to move out and requested for Kong Lin's help to search for hotels. Kong Lin managed to find one for us in such a short notice. Kong is such an experienced tour guide. We are very happy and satisfied with his explaination on all places we visited, especially the Mutianyu Greatwall. 
Kong Lin is an English speaking tour guide, as such we find it very easy to communicate with him. The fees charged is also not expensive at all.
We HIGHLY recommended such a responsible tour guide. Most importantly he has very good attitude. We APPRECIATED his contribution.