The special advantage of the half-round gutter from Marley is the cam-groove system:

Due to the material, gutters can expand when exposed to heat. The Marley cam-groove system compensates for this linear expansion: The cam of the connecting shell engages in a groove in the rear bend of the gutter. This lock limits expansion with temperature changes and prevents the gutter from denting or sliding apart.

The cam-groove system is integrated in the RG 75, RG 100, RG 125 and RG 150 half-round gutters.