This single wheel electric trailer dolly is priced at $879 and includes a coupler. It bolts to your trailer frame. (no drilling) necessary. The dolly utilizes a 1/4 horse a/c motor. Out of 537 dollies sold in 2003, 4 were single wheel dollies of which 3 had to be replaced with 2 wheel dollies because of a lack of traction and stability. Local customers are welcome to try them but in general, single wheel dollies have severe limitations.