All BONES WHEELS unique formulas are solely developed and produced in our own manufacturing plant located in Santa Barbara, CA. Using drastically different physical and engineering properties for each formula, BONES creates unique urethanes for specific applications of skateboarding. Street Tech Formula (STF) is specifically engineered from top quality components to obtain all the best properties necessary for the ultimate in street wheel performance. BONES WHEELS has created a wheel with a substantially higher rebound for more speed and amazing slide capabilities while maintaining a resistance to flat spotting well beyond any standard wheel. The technology behind STF is proven. The results speak for themselves. Skatepark Formula (SPF) is very high quality urethane specifically formulated to resist flatspotting on slick or smooth surfaces while maintaining a higher rebound for a quicker response and a faster roll. Skatepark Formula has a high resistance to abrasion while not compromising hardness and slide ability. Simply put… Skatepark Formula wheels grip better on slick surfaces, are almost impossible to flatspot, and are the fastest, longest lasting wheel on the market today.