20x28x5-R21-NBR Rotary Shaft Seal - Nitrile Rubber (NBR) Metric 20 x 28 x 5

20x28x5-R21-NBR Rotary Shaft Seal - Nitrile Rubber (NBR) Metric 20 x 28 x 5

Oil Seals or Rotary Shaft Seals are designed to provide a barrier to retain lubricant and to keep out contamination. They are available in metric and imperial sizes with a variety of sealing lip arrangements the most common of which are:

• R21 - Single Sprung Lip
• R23 - Single Sprung Lip with the addition of a wiper lip to help keep out contamination

Oil Seals are constructed using a steel case which is usually covered in rubber. Various materials are available the most common materials are:

• Nitrile Rubber (NBR) - Temperature Range -40 to +110 degree C - Usually coloured Black
• Viton Rubber (FPM) - Temperature Range -30 to +225 degrees C - Usually coloured Brown
• Silicone (SI) - Temperature Range -60 to +225 degrees C - Usually coloured Red