Egon,I know sch. 40 is not sch 160,nor is it sch 80. Henskin,,,I call it stovepipe,,,generally about sch 10 or something around there,,,Yeah,mag partical,,,thing about that is you gotta have a mag machine,,which costs money,,,,them p.t. kits ain't that much,,and in my opinion p.t. is the best way to find surface cracks,,not the fastest and it is messy,but its cheap,simple,,still gotta do it right,but,,,,,thingy