Wooster Mini-Koter 4" rollers have a metric core size for use with the Wooster R012 Mini-Koter roller frame. Best-quality roller fabrics offer excellent paint pickup and a very smooth finish. Use with the Wooster Mini-Koter roller 4" frame when painting tight areas behind radiators, pipes or toilet tanks and other narrow spaces where a brush or regular roller won't reach. Use the 1/4" nap mohair blane roller cover in enamels, varnishes and polyurethanes on smooth surfaces.