Gb1235-76 is the old national standard, O-ring representation method: OD x-ray diameter

GB3452.1-92 is the new GB, O-Ring representation method: Inner diameter X-ray diameter

Select O-Ring, the main look is O-ring outside diameter for sealing or inner diameter for sealing, two standards can be converted to each other, the same size can be common.

O-Ring O-Ring (o-rings) is a circular rubber ring with a cross-section, which is O-shaped, and is called an O-shaped ring. It began to appear in the 19th century century, when it was used as a sealing element for the steam engine cylinders.

Because the price is cheap, the manufacture is simple, the function is reliable, and the installation request is simple, O-ring is the most common mechanical design for sealing. The O-ring withstands dozens of kpa (thousands of pounds) of pressure. O-Rings can be used in static applications or in dynamic applications where there is relative movement between parts, such as the shaft of a rotary pump and the piston of a hydraulic cylinder.