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I am offering highly durable fluorosilicone o-ring kits for your various fuel caps. Please PM me or respond to this thread with your interest to include type and quantity. I will PM you to get your shipping information and arrange payment. These fluorosilicone o-rings offer superior durability to help your fuel caps keep the fuel in and to keep water out compared to your less superior rubber nitrate o-rings, which have to be replaced frequently. I will be offering kits for Shaw 531/431 caps, Shaw 416 caps, Shaw 457 caps, Gabb caps, and D’Shannon 15 gallon screw type fuel caps. Prices and contents are below. These prices also include shipping. CSOBeech has a great writeup on these o-rings at http://www.csobeech.com/fuel-caps.html. Installation is pretty straight forward but there is additional guidance on CSOBeech. Kits provide standard aircraft parts acceptable under 14 CFR §21.9 for a FAA certificated mechanic to install two military specification fluorosilicone type o-rings on Shaw 531,457, 431,416, or Gabb style fuel caps. Kits are eligible for installation by a licensed mechanic as a minor alteration under 14 CFR §1.1 and §21.93(a) as it has “no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness” of the aircraft. No STC, Form 337 submittal or FSDO field approval is required per FAA Order 8900.1 Figure 4-67. A §43.9 airframe logbook entry is sufficient to document this alteration and return the aircraft to service. Fluorosilicone are a much more durable material and will last longer than original Buna-N (Nitrile) rings found in Shaw and Gabb fuel caps. Fluorosilicone can withstand a broader range (-100 to 350 degree Fahrenheit) whereas Buna-N has a lower temperature range (-70 to 180 degree Fahrenheit). The manufacturers of the fluorosilicone o-rings are ISO17025 certified. Fuel caps should be inspected for continued airworthiness per your respective aircraft repair manual. I installed all new fluorosilicone o-rings on my four fuel tanks on my M35 Bonanza about a year ago and I have not had water in my tanks yet. My cousin left the Bonanza out on the ramp during monsoon season in Panama City Beach FL, this summer and water got into the static lines but nothing in the tanks! Not only were the old rubber nitrate breaking down on the big o-rings, the little ones were in poor shape too. Kits Available: The kit includes both the outer and the often overlooked inner plunger ring. If either are not working correctly, they can let water into your fuel tanks. Each kit also includes the correct cotter pins for the castle nut on the bottom of your fuel caps. - Shaw 431/531 fuel cap kit - $12.50 each o M25988/1-338 – big o-ring o M25988/1-010 – small o-ring o MS24665-298 – cotter pin - Shaw 416 fuel cap kit - $12.50 each o M25988/1-232 – big o-ring o M25988/3-010 – small o-ring o MS24665-132 – cotter pin - Gabb fuel cap kit - $15.00 each o M25988/1-339 – big o-ring o M25988/1-110 – small o-ring o MS24665-298 – cotter pin - D'Shannon 15 Gallon Screw Type Fuel Cap Kit - $8 Each o 2x o-ring replacements per kit Payment Details: I can take payment via PayPal, Popmoney, Square, or you can mail me a check. PM me for my mailing address for a check. PayPal handle is gallagher.394 at gmail.com and Popmoney is 419 357 0043. Further Information: If you’re not sure of your fuel cap type, snap a photo of the top and bottom, and then email me at gallagheraviationllc@gmail.com.