Felt ring seals are simple but efficient seals for use with grease lubrication. They can be operated at peripheral speeds of up to 4 m/s (800 ft/min). The seals can be used at higher speeds, but a small gap forms between the felt and the shaft. As a result the seals become non-rubbing gap-type seals. For pillow block housings with bearings on adapter sleeves and shafts not exceeding a surface roughness of Ra 3.2 μm, the felt ring seals are split. Oil-impregnated felt is inserted into Light Alloy half-rings and the seals inserted into the grooves of the housing. The rubber O-section cords should be put into the grooves first as they prevent the seals from turning. For bearing with a 13mm diameter.