Convoluted wafers have a wavy, convoluted design. The inside ring of the wafer gets pressed to make the convoluted shape. There are no spacers needed with convoluted wafer.  There is, however, a specific way they need to be installed. Once you get the placement right, convoluted wafers are much easier to install as there is no need for a spacer.

Flat profile sweeper wafer brush rings with a synthetic core and fill material. Available in standard core and brush diameters to fit all common machines.  

Steel Profile Brush Rings are available with a synthetic or steel wire for mounting to a roller brush or sweeping roller. Synthetic brushes are ideal for removing leaves and dirt, but combined with steel brush rings, they retain the flexibility to sweep, but with toughness to remove stubborn dirt and snow.