【Compatible with Perko 540 Series Deck Filler Caps】Fits Perko 540/0540 Series fuel, diesel, water, and waste filler caps. Suitable for threaded aluminum and stainless steel ports on fishing boats, sailboats, and other vessels. Great for regular maintenance or seasonal use of marine fuel fill o'rings and Perko deck fill o-rings 【Replaces Part Number 54000099B – Ideal for Gasket Replacement】Direct replacement for Perko 54000099B filler cap o-rings. Commonly used when restoring seal performance on older caps or during spring checkups. Keep spares onboard to prevent fuel or water leaks mid-trip. Also compatible with marine deck fill gaskets and Perko fuel cap gaskets 【Marine-Grade Oil-Resistant Rubber Material】Crafted from flexible oil-resistant rubber that performs well in marine environments. Helps reduce leaks in boat fuel filler caps, diesel tank inlets, and deck waste fill ports. Withstands saltwater, UV rays, weather exposure, and frequent replacement of marine fuel tank fill o-rings 【Approximate Size: 1.75" Inner Diameter × 0.14" Thickness】Each O-ring measures about 1.75 inches ID and 0.14 inches thick (44.5mm × 3.5mm). Compatible with Perko 540 series fuel cap gaskets, marine fuel fill o'rings, and boat fuel fill o-rings. Tool-free installation makes replacement quick and simple 【5-Pack for Replacements, Spares, or Multi-Cap Use】Includes five deck fill O-rings for gas, diesel, water, or waste systems. Use to replace worn gaskets or keep in your marine repair kit as emergency backups—ideal for sailboats, yachts, and vessels that use Perko fuel fill o-rings and marine deck fill gaskets 【Support When You Need It】If you have any questions about compatibility or installation, contact us via your Amazon order. We’re here to help 54000099B O-Rings have an inside diameter of approximately 1-3/4“ and are slightly over 1/8” (0.14") thick. Dimensions, tolerances, and materials are an exact OEM match for marine gas, diesel, water, and waste fill systems. Whether it is performing boat maintenance or timely replacing aging parts, this seal can help you cope with the needs and keep your boat running safely. Choose 54000099B seal to make every voyage more secure and reliable!