I have a Mankey strap, as others have mentioned I find it a bit stretchy to hold a heavier watch securely. I prefer an Erika's Original, the old style made for fixed bars. The material is much stiffer and holds the watch more securely. You have to specify "old style for fixed bars" since they have a newer style that runs behind the watch head and secures with a screw.
In the photo there is a small metal keeper missing that goes on the six o'clock side that I forgot to fit the first time I installed the strap and took the photos. It slides to the buckle and secures the strap from slipping once you've adjusted it for size.