This is general product-selection guidance, not engineering advice. Confirm the final product and specification for the application.
Photograph the application
Include an overall view and close-up images with a ruler or scale reference.
Record all dimensions
Measure inside diameter, outside diameter, wall thickness, profile dimensions, length and quantity as applicable.
Explain how it is used
Describe the equipment, movement, load, pressure, temperature and environment.
Send a sample or drawing
For profiles and mouldings, a sample or dimensioned drawing often provides the clearest reference.