{HEAD ~ The viewing hole} is of {TAIL ~ a predetermined size} so as to preclude convection flow sufficient to cook food, whereby the food will cook by radiant heat only 
is of
{ HEAD ~ The viewing hole } is of { TAIL ~ a predetermined size } so as to preclude convection flow sufficient to cook food , whereby the food will cook by radiant heat only
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH