Let me tell you, these flap discs have become my go-to for quick metal prep jobs. The first thing that surprised me? That fiberglass backing - at this price point, I was expecting flimsy plastic like most budget discs. The vibration absorption is noticeably better when I'm grinding down rusty truck fenders.
The Type 29 bevel design is where these really shine. Last weekend I was restoring an old iron gate with intricate scrollwork, and being able to angle the grinder let me get into those tight spaces without switching tools constantly. The 40-grit discs chew through paint and rust like butter, though fair warning - wear a mask unless you enjoy coughing up black dust for hours afterward.
Storage is my only gripe. Like others mentioned, I had to Sharpie the grit sizes on each disc after opening the packages. Pro tip: Keep them in separate coffee cans once marked. The 120-grit discs leave a surprisingly smooth finish - not mirror polish smooth, but good enough that I can skip an extra sanding step on most projects.
For less than $1 per disc? Absolute steal. They're not going to last as long as premium brands when grinding hardened steel all day, but for my weekend warrior projects restoring old tools and furniture, they hold up just fine. Just bought my second set because at this price, why not?