I purchased Grip Studs 3000A (Medium 3.5mm protrusion) from Grip Studs with carbide tips 3 years ago when I noticed them on eBay. I put them in the soles of my Bogs winter mid-calf boots for dedicated wear to snow blow the driveway, walk the dog or take the recycling down the icy driveway in the winter. They have performed admirably and I can say that I have not slipped once. With moderate wear in 3 winters, the carbide tips now show moderate wear, but all studs in place. I just re-ordered a set of Aggressive studs (4.4mm protrusion) as they are now available from Grip Studs website and sound even more suitable to Minnesota's icy driveways and walkways than the Medium Grip Studs.