Petty Officer 1st Class Rafael Castro, leading petty officer with Dental Detachment, Alpha Surgical Company, Combat Logistics Regiment 15 (Forward), 1st Marine Logistics Group (Forward), volunteers to have blood drawn during a Walking Blood Bank pre-screening at the Combined Aid Station, Camp Leatherneck, Afghanistan, Nov. 20. More than 140 participants volunteered to have blood drawn for testing. Once approved, donors may be called upon at any time to give blood if additional blood supplies are needed.