Check the listing for details. Hydrometer Rubber Replacement Kit - Bulb, Cork, Tip, Natural Red or Nitrile. Condition: New. Listed at 19.99 USD. These Replacement Rubber Kits will rejuvenate and keep your hydrometer sets in good working condition. Use this Red Natural Rubber Kit to replace cracked and dry-rotted rubber on your battery, antifreeze, and other sets. Use our Black Nitrile Rubber set for your API, diesel, fuel, and Nitromethane testers. This item is not intended for use with other brand testers. For best results, use only Brady Instruments brand testers. About Us: Free shipping to the lower 48 states only. If you have any questions about our products, message us. We have trained technicians waiting to answer your questions!Our hours of operation are Monday thru Thursday 7 AM-5 PM EST. HAND-MADE, PRO-GRADE & USA-MADE Check out our eBay store for other great products!