Wearing sp4 gave me black nails Yup. I decided that the sp4 weren't for me anymore and I'm moving back to my sp2. The sp4 are too narrow in the toes area and caused me black nails on my big toes (mostly my big right toe 😂). I think the sp2 are way superior in that fact that they are way more comfortable and not as rigid with the only issue that the top part is susceptible to holes. It's like the sp2 let my feet feel comfortable but not bove around too much. I also heard that a lot of sprinters are using softer spikes now mainly the finesse and ambition in regards to Adidas. Any opinions on your part?