STACK PACK COMPATIBLE – Fits with select FLEX STACK PACK tool boxes. Ideal for the Rolling Tool Box (FS1101), Medium Tool Box (FS1102), and Suitcase Tool Box (FS1103). Level holder opening size: 2 1/2 inches by 1 5/8 inches EASILY TRANSPORT LONG ITEMS – Secure and transport long items like levels and conduit benders DURABLE CONSTRUCTION – Made from a hard plastic known for its durability to keep your tools secure QUICK INSTALLATION – Easily screws to tool box for durable, secure connection FULL RANGE COMPATIBILITY – STACK PACK toolboxes, organizers, accessory cases, and toolbox attachments are endlessly configurable across the full STACK PACK system