Grease Seals are bespoke products used to protect and prolong the service life of aircraft wheel bearings. They are usually custom designed rubber rotary lip seals, designed to restrict bearing grease loss and prevent water and dirt ingress, during normal service and cleaning conditions. Snap-fitting Polytetrafluoroethylene (PTFE) variants are also available. Grease Seals can be located in a number of ways either designed to: incorporate retention features, press-fit into the wheel hub or axially locate with circlips or sleeves. They have been designed and tested to include 1 mm variances in axial bearing face location. Grease Seal types are offered for both inboard and outboard-of-bearing positions. They can also be designed specifically to aid their assembly as original equipment or insubsequent retrofitting.