NEW READY TO INSTALL. VERY SIMPLE DESIGN. EASY TO USE. COMES WITH MOUNTING INSTRUCTIONS. THIS IS A RED TENSIONER. Fits front and rear cylinders, if you need 2, buy 2. This tensioner is Blue. This fits Aprilia: - 2006 to 2012 SXV RXV MXV 450 550 REPLACE THAT OLD AUTOMATIC TENSIONER THAT WILL EVENTUALLY FAIL YOU. HAVE COMFORT KNOWING THIS ONE CAN NOT COLLAPSE UNDER STRESS. - CHEAPER THAN A NEW STOCK AUTOMATIC / PROBLEMATIC TENSIONER. THIS MANUAL CAM CHAIN TENSIONER IS DESIGNED TO REPLACE THE AUTOMATIC AND HYDRAULIC TENSIONERS ON HIGH PERFORMANCE ENGINES. THE AUTOMATIC ADJUSTERS CAN BACK OUT WHEN THE THROTTLE IS CLOSED SUDDENLY AT HIGH RPM. THIS ALLOWS THE CAMS TO GO MOMENTARILY OUT OF TIME, AND CAN RESULT IN BENT VALVES AND SERIOUS ENGINE DAMAGE. HYDRAULIC TENSIONERS HAVE A TENDENCY TO PUT TOO MUCH TENSION ON THE CHAIN GUIDE UNDER HIGH RPM (HIGH OIL PRESSURE CONDITIONS), RESULTING IN PREMATURE WEAR. BOTH PROBLEMS CAN BE ELIMINATED WITH THE INSTALLATION OF THIS MANUAL TENSIONER. NO MATTER WHAT THE ENGINE DOES, THE CAM CHAIN TENSION WILL REMAIN CONSTANT. THIS MANUAL CAM CHAIN TENSIONER IS A MUST FOR ANY KIND OF PERFORMANCE RIDING. THIS MANUAL TENSIONER IS CNC MACHINED FROM BILLET ALLOY TO EXACT TOLERANCES FOR PERFECT FIT.