A spring holds these tighter than other toggle pins so they won’t slide or rattle around in the hole. No need for a separate cotter pin, the toggle swivels so you can insert the pin into a hole and then swivels back to lock. These have a flat, low-profile head to fit in tight spaces. They're less likely to get in the way than loop- or ring-grip pins but aren’t as easy to grab if you want to remove them frequently.