What makes good rebounders

It is interesting to watch good rebounder and wonder what makes one. Sidney Moncrief is the all-time leader at Fayetteville, and I heard that his leaping ability and particularly his timing on his jumps was what made him good. Rashad Jones-Jennings said his ability to anticipate how the ball would come off the rim helped him, and his coach said his fundamentally-sound technique and just pure desire had a lot to do with it. He was far from being the best athlete and leaper even on his team. Wes Unseld was one of the smallest NBA centers in the modern era, and yet he was a dominant rebounder. Obviously, positioning is a key, also.