Should be a sticker on the mast of who made it. Contact them for parts. I found my 2008 U.S. Spars catalog. My B323 has mast Z401 (p 13). I had on hand 2 OEM cleats when one broke on a friend's 331. My cleat fit her 2 mounting holes, so she used it. Cleat #4586 is plastic, and used to be $11.18. The metal # 1081 (I suggest this one) used to be $21.00. While I was at it, I got another cleat to put on the boom, opposite the one already there. These are the cleats somewhat squared off on the horns.usspars.com 800-928-0786