Just picked up this peep today. Pretty cool, the actual peep alone is 1/4 inch. It has the 1/8, 5/32, and 3/16 apertures that come with it. The apertures are a silicone and can be pushed out so you can change them for different shooting styles. The silicone apertures are 9 to a pack and come in 3 different colors, red, flo-green, and black. I put the peep in my string this afternoon and drew my bow with it, all is well so far. I havent had the chance to shoot with it in yet, but will tomorrow. I will do a small review on it once I have shot with it a little while. I was having problems with the right peep size for me and my sights. When I drew back and looked down thru the peep, it was perfect. The aperture is just the right size and matched up with my sight housing. We will see how well it holds up after I have shot it a few times. I will keep ya posted.