All air assist...no hydrolics needed. It also has all the hookups on the back to add a third flip up axle . This trailer has only around 5,000 miles on it. Only hauled one 40,000 lb combine, all other loads were smaller tractors and combines from auction sales for different people. Never anything loaded on the wood deck that did not have tires. No damage to the wood deck, nothing is bent, and everything works like new. . The air assist is the slickest thing I have ever used for a trailer. A brand new one exactly like this one is around $90,000. Trailer is in Grand Forks.