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 WHAT'S INCLUDED - (1) FLEX STACK PACK Level Holder, (2) FLEX STACK PACK Corner adaptors, fasteners for installation FULL RANGE COMPATIBILITY - STACK PACK toolboxes, organizers, accessory cases, and toolbox attachments are endlessly configurable across the full STACK PACK system