We are a leading global designer, producer and marketer of a wide range of electromechanical power transmission motion control ("PTMC") products. Our technologies are used in various motion related applications and across a wide variety of high-volume manufacturing and non-manufacturing processes in which reliability and precision are critical to avoid costly down time and enhance the overall efficiency of operations.
We market our products under well recognized and established brands, which have been in existence for an average of over 85 years. We serve a diversified group of customers comprised of over 1,000 direct original equipment manufacturers ("OEMs") including GE, Honeywell and Siemens, and also benefit from established, long-term relationships with leading industrial distributors, including Applied Industrial Technologies, Grainger, Kaman Corporation and Motion Industries. Many of our customers operate globally across a large number of industries, ranging from transportation, turf and agriculture, energy and mining to factory automation, medical and robotics. Our relationships with these customers often span multiple decades, which we believe reflects the high level of performance, quality and service we deliver, supplemented by the breadth of our offering, vast geographic footprint and our ability to rapidly develop custom solutions for complex customer requirements.
Our product lines involve a large number of unique parts, are generally delivered in small order quantities with short lead times and require varying levels of technical support and responsive customer service. Many of our OEM customers incorporate our products into their designs of their equipment, helping to generate high switching costs and foster brand preference. As a result of these characteristics, the essential nature of our products and the wear to which many are subjected, we generate a significant amount of recurring revenue with repeat customers. Our large installed base generates significant aftermarket replacement demand, which we estimate accounted for approximately 32% of revenues in 2018 on a pro forma basis giving effect to the Fortive Transaction.