- The self-aspirating mechanism works by a little bump at the end of the syringe compressing the diaphragm of the anesthetic cartridge during injection. - When the pressure of injection is released there is the relaxation of the diaphragm, thus creating negative pressure. - Stainless steel. Contents: - 1 syringe 1.8 ml. - 2 heads. **For further product information, please contact Chat Support**