Crystal Cores feature Ricta's new optically clear high-performance 95a urethane. 95a high-performance urethane offers a more forgiving durometer for rough terrain with easy, consistent slides you'd normally only get on harder wheels. Ricta's latest core design provides optimal speed, reduced rolling resistance, and maintains shape integrity on landings for easy rollaway. Available in 52, 53, 54mm Wide. Ricta's latest core design provides unique speed, reduced rolling resistance, and maintain shape integrity on landings for easy rollaway. Available in 52, 53, 54mm Wide.