This is a set of oil gallery plugs for 1JZ and 2JZ engines. Whenever we rebuild a JZ engine we pull these plugs out, and it is surprising how much metal debris you'll find in there! ESPECIALLY when a block is machined for billet main caps, there will be all sorts of metal in there, just waiting to ruin your brand new bearings, cams, and turbocharger. Even when the machine shop says "the block was hot tanked", the plugs need to be removed, and the galleries cleaned with a gun barrel brush. It is impossible to get all the debris out without removing the plugs.

Aaron's Tip: I made a 1/4-20 threaded socket attachment for my slide hammer so I can mig weld studs to the stock gallery plugs, and then slide hammer them out. Then once I pull out two on one side, I use a long piece of 1/'2" steel rod to quickly hammer out the balls at the other end. Walmart sells an inexpensive gun barrel cleaning kit that works great for cleaning out the block oil galleries.