Shars 6" Fully Machined Threaded Back Plate 1-1/2-8 For 3 or 4 Jaw Self Center Chuck 202-6109 S

It fit just fine on my new 6 inch chuck. There was a very minimal amount of milling necessary. With a small amount of adjusting the run out was between 1 and 2 thousands which is plenty good for my hobby type of work.