From the same company that brought you the HUGELY popular 'Poison' hybrid wheel...Now comes BOOM!Atom Wheels is a huge proponent of evolution and we've pushed the envelope over the past year to develop a new, high-performance wheel that works on cement, asphalt, sport court and MANY wood surfaces.BOOM provides grip with a controlled slide. The perfect wheel for all levels and all positions, you will want a set of BOOM wheels in your bag! Firm: recommended for all slick surfaces but also has slide capabilities for plow stops. XFirm: recommended for surfaces with more grip but skaters looking for additional roll with grip and a controlled slide. XXFirm: recommended for grippy surfaces, skaters wanting maximum roll with controlled slide on sticky surfaces.