Starrett A5 Hole Saw Arbor Extension Bar, 12" Length, Fits 1/2" Chuck Go to amazon.com Related posts Best holesaw extension FeatureHole saw arbor extension barSuitable for use with any arbor with a 7/16-inches shank size12-inches length DescriptionStarrett hole saw arbor extension bar fits 1/2-inches chuck. Suitable for use with any arbor with a 7/16-inches shank size. 12-inches length.