Spark Plugs Detect earplugs have been specially developed for use in the food industry. The earplugs and cord are metal detectable and coloured blue for high visibility. Thanks to the specially developed foam formula, Spark Plugs Detect earplugs offer the optimum combination of stability and softness. They are easy to roll up and expand at just the right moment when inserted into the ear canal. There, they maintain a secure, sealing fit without exerting pressure on the ear.