First, the two rollers gives a pulley function with a large radius. This protects the line for bending demage during the pulling of line.
The second is that the clamp is designed for assembly and disassembly with live-line-tools. This opens up new and significantly more efficient construction methods. Tightening the clamp can be done after the new line is energized.
The third factor is that the pulley-clamp has no separating parts. This means that the clamp can be opened and closed without the risk of losing componenets/parts during the construction process.
It is also worth mentioning that the concept allows “recycling”. That is, when changing old to new conductor. You do not even have to climb the posts to make this. Clamps loosened with live-line tool. The old conductor attached to the new and pulled through the pulleys. The line can be energizes prior to fixing the conductor using live-line tool. This gives a very short outage and saved costs. This new method reqiuires less manpower/crew compared to of traditional construction method.