Check the listing for details. Bones Hardcore Medium Bushings 91a - Yellow/White (Set of 4). Condition: New. Listed at 10.00 USD. Bones Hardcore Medium Bushings 91a - Yellow/White (Set of 4) The HardCore insert in the center of BONES bushings connects the two sides of each bushing together by bonding them to the HardCore insert. When the hanger web squeezes one side of a HardCore bushing, that side of the bushing reacts just like a normal bushing, but the chemical bond between the HardCore and the cushion keep the bushing from being squeezed out the other side. It actually increases the resistance to turning because it is held in place by the HardCore insert. This means basically that BOTH sides of the BONES HardCore Bushing are resisting your turning force. That’s why we call BONES Bushings the first double action truck bushings. Features: Patented Double Action bushing Chemically bonded core insert High rebound urethane Hardness: 91A With BONES Bushings, you will notice a number of positive improvements in the performance of your trucks. There is no break-in period. Just put them in, adjust and skate. Your trucks will be more responsive. Increased truck performance Improves your skating experience. Your turns will be smooth and positive, not floppy or rigid. 3 Hardnesses: Hard Bushing: 96A, Medium Bushing: 91A, Soft Bushing: 81A At SkatesUSA our primary goal is to give our customers the best deals on skateboards, longboards, scooters and bikes at the lowest price. That is our commitment to you, our valued customer.