These are replacement earcup yokes for the Bose X aviation headset. Made in the USA, these are far stronger, longer-lasting and less expensive than other aftermarket or the factory versions. They will last the life of your headset, guaranteed. Both sides are included. They are made of a high-end annealed carbon fiber-reinforced composite that is much stronger than all other resin-based aftermarket parts and exponentially stronger than the cheap plastic used in the original part. The weak points of the OEM design where your original yokes have degraded and cracked have been completely redesigned using SolidWorks software, the same software Bose used with designing the original headset. They are then produced by a company located in the US who are experts with manufacturing aerospace parts. They simply will not break even under extreme stress (the rest of the headset will fail before this part does – we dare you to try to break it!) They are not weakened by UV exposure or age. Simple install using just a Phillips head screwdriver. This will be the last set you need to purchase for your Bose X headset. Stainless steel standard Phillips head mounting screws are included (no need for special tool).