Old Man Emu engineers specialize in 4WD suspension systems, and it's this experience in setting the most appropriate valving that really differentiates the Nitrocharger Struts from the competition. While Old Man Emu Nitrochargers will improve overall performance when fitted with standard springs, more substantial benefits can be achieved when fitted in conjunction with Old Man Emu springs, for a complete, integrated 4WD suspension system. All Old Man Emu Suspension systems are engineered, developed, tested and manufactured entirely in - house and come with a 3 - year warranty.