There are 4 different grip safetys that you can pick
pivoting, full profiled tail
non-pivoting, full profiled tail
pivoting, thumb relief profiled tail
non-pivoting, thumb relief profiled tail
thumb relief profile is like those STI grip safety with the left and right side cutouts. I use them and like them much better than the regular, full profiled tail.
See
http://www.sviguns.com/1101.php?indx=19
It is not listed on the system, but you may want to decide which one you want and include it as comment.