3/16 to 1/4 diametere is good for hunting..Alot of the quality sights have a ring around the pin housing..if you line the ring diameter with the peep diameter and center your pin from there you will be a much more accurate shooter..I have a G5 meta peep that is 3/16 diameter and it works very well for me even in low light..Also agree with pin size..my 25 and 40 yrd pins are 0.19..50 thru 70 are 0.10