The Leg Curl / Extension Attachment connects to the SCS-WB & FIDB benches. Use the attachment to comfortably execute leg curl and extension exercises. The built-in weight horn allows you to add weight plates for added resistance. This attachment also ties into the FT2 cable resistance system if purchased with the FT2 Leg Kit option as well.The Leg Curl / Extension Attachment connects to the SCS-WB & FIDB benches. Use the attachment to comfortably execute leg curl and extension exercises. The built-in weight horn allows you to add weight plates for added resistance. This attachment also ties into the FT2 cable resistance system if purchased with the FT2 Leg Kit option as well.