A needle set for a biopsy device is disclosed. The needle set includes an outer member, a cylinder lumen within said outer member, an inner member having a cannula and an inner lumen. The inner member is slidably disposed within the cylinder lumen. The biopsy device also includes a cylinder seal member that is disposed within the cylinder lumen and a cannula seal member attached to the outer surface of the cannula. The cylinder seal member and the cannula seal member define a vacuum chamber therebetween.
