Mast cartridges 100% E.O Gas Sterilized and individually packaged. Smooth edges eliminate additional trauma. Needles are made of 316 medical grade stainless steel. Precision assembly. Quality is ensured with meticulous 30-point inspection, including pin alignment and solder distribution. Membrane mechanism prevents ink spitback. Low profile housing & better ink flow & shaped on the inside. Mixed size, If you have the size request please send us email, or we send them automatically. Please leave a message which size you need, or will send in random.