(From the Squadron supplier): Helicopter Sea Combat Squadron 21 (HSC-21), nicknamed “Blackjacks”, is an aviation unit of the US Navy based at NAS North Island, CA. HSC-21 is made up of five expeditionary detachments that deploy aboard ships including Combat Logistics Force support ships, Hospital Ships and Amphibious Assault ships, among others. HSC-21 flies the Sikorsky MH-60S Seahawk helicopter currently. This is the yellow/black version of their squadron patch showing their mascot carrying weapons ready for delivery to the target. This patch does not come with velcro attached..