O-ring toric watch gasket 0.55 mm. Premium nitrile rubber for long-lasting sealing performance.
This O-ring gasket of 0,55 mm thickness is a precision sealing component used by professional watchmakers and serious hobbyists to restore the water resistance of mechanical and quartz watches. Manufactured from NBR rubber (acrylonitrile-butadiene) compounded around 70 Shore A, it offers the elasticity required to seat correctly inside a case-back groove while preserving long-term resilience against compression set, watch oils and the small temperature swings encountered on the wrist.
The O-ring gasket in 0,55 mm is the most common sealing profile on contemporary watches. Its toroidal cross-section concentrates the elastic load on a thin contact line, which keeps friction low when the case-back is screwed home and produces a self-energising lip whenever external water pressure rises. Properly installed and lightly coated with Moebius 8217 silicone grease, this gasket contributes to a depth rating commonly stated as 3, 5 or 10 ATM depending on the watch case geometry.
This reference belongs to a calibrated assortment supplied with a comprehensive inside-diameter range, so the watchmaker can pick exactly the right size for a case-back gasket, a crown gasket or a crystal gasket on bezel-loaded movements. The grade chosen here is a workshop-tested NBR rubber (acrylonitrile-butadiene), identical in spirit to the gaskets fitted by mainstream Swiss and Japanese factories on three-hand divers and dress watches.
A gasket of 0,55 mm should be selected whenever the original cord has lost section, flattened into the groove of the case-back, taken a permanent compression set or hardened to the point of leaving witness marks on the case. In normal use, the inspection interval is every battery change for quartz pieces and at every full service for mechanical watches — typically every four to six years. A gasket found dry, cracked or twisted must be replaced immediately, regardless of the apparent watertightness.
This thickness is also the right choice for replacing a worn crown gasket of the same cord on stems that drive a screw-down crown, and for rebuilding the seal under a pressed mineral crystal where the case maker originally fitted an O-ring between the bezel and the case middle. Many Rolex, Omega and Seiko service kits list gaskets in 0,55 mm for these exact positions.
Each batch of gaskets is checked dimensionally with a profile projector and randomly tested for hardness on a Shore A durometer before shipment. The NBR rubber (acrylonitrile-butadiene) compound is sourced from a European supplier with full RoHS and REACH compliance, and the gaskets are stored away from ozone and direct sunlight to preserve elasticity. For watchmakers who service vintage chronographs or warm chronometers, an alternative FKM / Viton fluoroelastomer variant and an EPDM variant are available on request, both compatible with Moebius 8217 silicone grease.
Measure the cord diameter (thickness) and the inside diameter of the original gasket with a caliper after removing it from the case-back groove. For a 0,55 mm cord, the assortment offers a continuous range of inside diameters; pick the one that drops freely into the groove without bunching.
Many screw-down crowns share the cord diameter with the case but use a smaller inside diameter; verify the crown gasket size in the brand's technical sheet. If the cord matches, this reference fits; otherwise pick the same 0,55 mm cord in the correct inside diameter.
Yes. NBR rubber (acrylonitrile-butadiene) is the standard compound paired with silicone-based watch greases such as Moebius 8217 silicone grease; the grease swells the polymer marginally and seals it without attacking it. Avoid mineral oils, brake fluids and aromatic solvents.
O-ring toric watch gasket 0.55 mm. Premium nitrile rubber for long-lasting sealing performance.
