Experience the COREFX Advanced Toner for the most versatile and dynamic workout of your life! Every COREFX Advanced Toner features a premium polypropylene covering for extreme protection of the resistance tubing core. The resistance tubing covering helps to not only protect the rubber core but it also helps to prolong the life of the resistance tubing by preventing athletes from over-stretching the resistance tubing. The COREFX Advanced Toner is the perfect fitness equipment for intense personal training sports conditioning and boot camp workouts. This resistance tubing is made from only the highest quality materials to meet the demands of serious athletes all over the world. These are perfect for sports conditioning personal training and boot camp workouts to help increase strength and build toned lean muscle FAST!