This is the lighter cousin of the 70×45, same F17-rated Victorian Ash, just trimmed down in depth for jobs that don’t need the extra bulk. Builders reach for this size when they want structural-grade strength without adding unnecessary weight or cost to a frame, particularly on smaller spans or secondary framing members. It’s kiln-dried, so it holds its shape well once it’s in the wall or roof, and it machines cleanly if you need to notch or trim on site. Because it’s still F17, you’re not losing the strength rating you’d get with a bigger section, you are just sizing it to the job. Good stock item for renovators matching existing framing, and popular with smaller builders who don’t want to over-order timber for light-duty structural work.