【2026 Upgraded】 You get 2 premium P322055 furnace vent safety switch thermostats in one pack, ideal for replacing worn-out switches and keeping a spare for quick maintenance. This upgraded version enhances safety and performance for Williams HVAC system. 【Perfect Fit for Williams HVAC Systems】 Expertly designed to be fully compatible with Williams heating systems, including Monterey Counterflow Top Vent models 3509821 and 3509822. It integrates smoothly without the need for extra adjustments or modifications to your furnace setup. 【Critical 260°F Overheat Protection】 Triggers an immediate system shutdown when vent temperatures exceed 260°F, preventing overheating, fire risks, and carbon monoxide leaks to protect your home and equipment. It resets automatically once temperatures return to a safe range for reliable operation. 【Durable & Long-Lasting Construction】 Made from high-quality heat-resistant materials, this thermostat switch stands up to harsh furnace environments and frequent temperature fluctuations. Its robust build ensures stable performance and reduces the need for frequent replacements. 【Easy Installation & Reliable Support】 Simple to install with basic tools, and our team is ready to assist with any questions about compatibility, setup, or performance.