I’m putting a 6” extension on Tracy’s RD-1B.  Craig Catto recommended only Saber Mfg for the expertise and precision in prop extensions – 817-326-6293.  It’s a fine piece of work.  I’m also transitioning to ½” bolts, ¾” lugs and 7” hub recommended for my 260 hp 20B and 66” 3-blade prop.  Tracy’s hub is 6 ¼, has 3/8 bolts and 5/8 (I think) lugs.

Al

For the record, the extension that I got through Spruce came from Saber, and I agree that it's an excellent piece of work.  It looks like you can save about $50 going direct. 

Rusty (oil scoop done, and I like it)