DENSO Twin Tip Spark Plugs K16TT With the launch of Nickel TT in 2010, DENSO’s innovative, TT Spark Plug technology is the outcome of years of Research and Development work at DENSO Japan’s engineering center, aimed at meeting the joint challenges of environmental protection and technical performance. The TT range offers: Improved fuel efficiency. Low carbon dioxide (CO2) and hydrocarbon (HC) vehicle emissions. Better acceleration and output. Consolidated ranges to cover the vast majority of EU car park. Advanced OE-quality technology available to a wider range of vehicles at an affordable cost.