Classic Rubber Products offers the seal industry's largest inventory of o-rings, which includes every standard and non standard size 0.5mm to 3000mm Inner Diameter. The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons.O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable, and have simple mounting