comprises a valve arrangement such a valve arrangement could be constructed so as to prevent cross contamination of the first and second medicaments contained in the first and second reservoirs respectively a preferred valve arrangement may also be configured so as to prevent back flow and cross contamination of the first and second medicaments in one preferred system dispense interface 200 includes a valve arrangement in the form of a valve seal 260 such a valve seal 260 may be provided within a cavity 231 defined by the second inner body 230 so as to form a holding chamber 280 preferably cavity 231 resides along an upper surface of the second inner body 230 this valve seal comprises an upper surface that defines both a first fluid groove 264 and second fluid groove 266 for example fig9 illustrates the position of the valve seal 260 seated between the first inner body 220 and the second inner body 230 during an injection step this seal valve 260 helps to prevent the primary medicament in the first pathway from migrating to the secondary medicament in the second pathway while also preventing the secondary medicament in the second pathway from migrating to the primary medicament in the first pathway preferably this seal valve 260 comprises a first non return valve 262 and a second non return valve 268 as such the first non return valve 262 prevents fluid transferring along the first fluid pathway 264 for example a groove in the seal valve 260 from returning back into this pathway 264 similarly the.