Finding the BEST Medium-Duty Stretcher Bar - 50" helps ensure that you start off with a great canvas. Only by starting off with the best materials, can you do your best work. Made of white pine that is knot free and kiln dried, this 50 inch stretcher bar is ideal for a variety of different weights and lengths of canvas. Surface friction is reduced due to the back edge being rounded. This edge is also designed to keep ghost impressions to a minimum by keeping the canvas at least 1/2 inch in between it and the stretcher bar.