This is a J-48761 tool meant to lock your flywheel and allow you to do timing chain and other various jobs on Nissan engines. This is absolutely a must have tool if you’re doing that job and is almost the only way you can get a harmonic balancer off. Also referred to as a ring gear stopper. Used once and worked like a dream. I don’t know how you can do a timing chain job without this tool. Paid $162. Asking $100 and firm!