The edge of {HEAD ~ the partial ball} is characterized by having a v notch to obtain {TAIL ~ desired valve characteristics} as well as to provide shearing actions at the sharp edges of the valve as it closes 
The edge of { HEAD ~ the partial ball } is characterized by having a v notch to obtain { TAIL ~ desired valve characteristics } as well as to provide shearing actions at the sharp edges of the valve as it closes
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH