Harman's line of Silicone Flangeless Masking Plugs is specifically designed to mask threaded holes, including the top thread, without masking the surrounding area. The tapered ribs and hollow core allow for many different size holes to be masked, regardless of the thread pitch. Will withstand 315 Celsius / 600 Fahrenheit.

Material: Silicone 
Application: Protects Threaded Holes (Including The Top Thread) Without Masking The Surrounding Area

When you're painting, plating powder coating or anodizing, these rubber silicone flangeless masking products are specifically designed to mask threaded holes and not the surrounding area. The tapered ribs and hollow core allow for many different uses on holes of various sizes, regardless of the thread pitch.