Superior 1 Ton chain fall on trolley. The rollers measure 3 3/4" in diameter. There are four sets of seven spacers to make the trolley assembly adjustable to accommodate I-beam dimensions of 3 1/4" to 4 3/4" wide. The pictures show the rollers set at both the widest and narrowest positions. The chain drop is 8 feet. This is a heavy, older, well made piece of equipment. It's located in Oakham, MA. Thirty minutes west of Worcester.