A smaller sight pin generally improves accuracy because the sight pin covers less of the target. You can’t shoot it if you can’t see it. A smaller sight pin is also harder to see. You eyesight determines how small of sight pin you can see. Generally, if you are shooting 3-D or targets you want a small aiming point because you are shooting at small circles. Hunters generally want something a little larger because it is easier to see a larger pin and you are shooting at a larger target. Hunting shots are usually closer than many target shots. Moving the sight pin further from your eye makes the pin appear smaller. You can move your sight out to its furthest setting for 3-D and move if in for hunting.

Don’t be confused by fiber size and sight pin size. Most fibers come in millimeters. 1 mm is about .040”. 3/4 mm is about .030”. Most also melt back the end of the fiber to lock it into the pin block. Most melt it back about .015”. A .040” fiber then becomes about .055”. To give you an idea about size, a piece of copy paper is usually about .0035” thick. Therefore a .040” fiber before it is melted back is about the same diameter as 11 pieces of copy paper. Pin size is entirely different than fiber size. Some manufactures advertise .030” or even .020” fiber, but they are in the same pin block as the .040” fiber. That means you have just as much of the target covered, but you have a smaller fiber so it is harder to see. Most pin blocks are about .075” - .090” thick. Generally a molded pin block can have a smaller fiber hole because a pin makes the hole in the molding process. A metal pin block is more limited because you have to drill the hole and you can’t find a drill bit that small. Breakage would be a real problem If you made a drill bit that small.