Home > Store: Order Now > Orings
Orings can be used as a "dam" to avoid getting First Contact Polymer on your optic retaining ring. The retaining rings sometimes do not fit snug to the optic surface and the polymer, being a liquid, may possibly flow under the retaining ring and may not peel out, leaving polymer residue at the retaining ring edge. This also holds true for optics retained from the backside; the polymer can flow under the retaining lip. View our Oring Flow Control document to see photos and a description of how the process works.

Orings are an excellent choice for telescope eyepieces and filters, camera lenses, and protecting the secondary mount gasket on SCT corrector plates and primary mirror baffle tubes. Orings can be used for nearly any mounted optic!
Sort By:
Page of 1
Orings - 3" to 3.875" OD (Sold Individually) Orings - 4" to 4.875" OD (Sold Individually) Orings - 1" to 1.875" OD (Bag of 5)
Orings sized 3" to 3.875" Outside Dimension (OD). Use to stop First Contact Polymer from flowing on or under optics retaining rings. Measure the Inside Dimension (ID) of your retaining ring to select the correct oring size OD from the drop down menu. Orings 3" to 3 7/8" are sold individually. Orings sized 4" to 4.875" Outside Dimension (OD).  Use to stop First Contact Polymer from flowing on or under optics retaining rings.  Measure the Inside Dimension (ID) of your retaining ring to select the correct oring size OD from the drop down menu.  Orings from 4" to 4 7/8" are sold individually. Orings sized 1" to 1.875" Outside Dimension (OD). Use to stop First Contact Polymer from flowing on or under optics retaining rings. Measure the Inside Dimension (ID) of your retaining ring to select the correct oring size OD from the drop down menu. Orings 1" to 1 7/8" are sold in bags of 5.
Orings - 2" to 2.875" OD (Bag of 5) Orings - Custom Size 5 To 10 Inches OD (Sold Individually) Orings - Custom Size 10 to 20 Inches OD (Sold Individually)
Orings sized 2" to 2.875" Outside Dimension (OD). Use to stop First Contact Polymer from flowing on or under optics retaining rings. Measure the Inside Dimension (ID) of your retaining ring to select the correct oring size OD from the drop down menu. Orings 2" to 2 7/8" are sold in bags of 5. Orings are used to stop First Contact Polymer flow on or under optic retaining rings (or retaining flanges if retained from backside). We will manufacture a custom sized oring to fit your optic.

Measure the Inside Dimension (ID) of your retaining ring, mirror cell, etc. to select the correct oring size OD and enter the size in the space provided. Custom size orings are sold individually.
Orings are used to stop First Contact Polymer flow on or under optic retaining rings (or retaining flanges if retained from backside). We will manufacture a custom sized oring to fit your optic.

Measure the Inside Dimension (ID) of your retaining ring, mirror cell, etc. to select the correct oring size OD and enter the size in the space provided. Custom orings are sold individually.