Caterpillar 2199057 O-Ring is a Hercules catalog product available from WQC Parts for hydraulic cylinder, seal kit, pump, motor, valve, and heavy-equipment repair applications. This listing uses Hercules part number CTC-2199057. Catalog description: O-RING (5). Product Details Hercules part number: CTC-2199057 Product type: O-ring or sealing component Reference brand/application: Caterpillar Approximate weight: 0.006 lb Use this product when your parts book, service manual, cylinder repair list, pump/motor breakdown, or existing component calls for CTC-2199057. It is intended to help restore sealing performance, reduce leakage, and support reliable equipment repair when correctly matched to the application. Fitment VerificationBefore ordering, confirm the CTC-2199057 reference against your OEM reference number, machine model, cylinder location, bore and rod size, pump/motor series, and serial-number range. Manufacturer names and part numbers are used for identification and fitment reference only. If you are unsure, compare the old parts, measurements, and parts-book callout before installation.