I have Simms Guides; one pair studded felts, and one pair studded Aquastealth. I really liked the Aquastealth better than the felts, and then two years ago, I installed additional tungsten studs on the Aquastealth, and NOW do I have a pair of great boots. The tungsten studs which Simms sells are screw heads, whereas the original studs in the boots were small pins. The additional screw heads did the trickl.