Strengthen your swing connections with the Standard 3/8" x 3" S-Hook. A classic of swing hardware, these are sure to slip fairly easily through the chain and seat to create a secure connection. Close them with the S-Hook pliers for maximum safety. S-Hooks require more attention that more common shackles, however, certain pieces such as the 5' Soft Grip Chain can only be used with them.
For a larger or smaller S-Hook, check out the Large End 3/8" x 4" S-Hook, Standard 5/16" x 3" S-Hook, and Large End 5/16" x 4" S-Hook.