The blister when in its piercing position is interposed between {HEAD ~ the delivery channel} and {TAIL ~ the connection channel}  
The blister when in its piercing position is interposed between { HEAD ~ the delivery channel } and { TAIL ~ the connection channel }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH