2 3/8” and the slots are 5/16”.
On the HS55 the skids are mounted on struts behind the housing. The new skids are way to large to fit in the original position. So I removed the old struts and skids and mounted the new skids to the main blower housing. I only had to drill one new hole for each skid, the second bolt was already there and available. Installation was quite quick.
Got the skids. I didn’t realize how bad the old ones were until I received yours. Wow.