From 247sports analysis of the 2018 NFL draft of OL:
Takeaway No. 1: Heavier isn’t better
The average height between the drafted group and the undrafted group was essentially the same, both at right around 6-foot-5. There was, however, a stark disparity in the average weights of the undrafted guys and the players picked within the first 100 selections. The average high school weight of those 20 plum selections was 284 pounds. The average weight of the nine undrafted top-100 recruits was 25 pounds heavier, at 309 pounds. We have high school weights for 17 of the 20 drafted prospects and only five were listed over 300 pounds. Among only nine undrafted prospects, five were over 300 pounds and seven were 290 pounds or heavier.
Takeaway No. 2: Athleticism indicators are everything
This is no surprise and it is consistent with the first takeaway. Offensive linemen that land in the NFL are athletes, not just wide bodies, and there are a lot of ways to sniff out an athlete beyond the film. Does an offensive lineman play defensive line too? Twelve of the prospects that ended up taken within the first 100 picks played significant snaps on defense (I could only verify that two of the nine undrafted played defense). We have high school testing numbers on six of the first 100 selections. The average 40 time was 5.24, shuttle was 4.77 and vertical was 27.1. The average numbers for the three undrafted prospects that we have data on were 5.7, 5.13 and 23.6, respectively.