Features a unique metal-on-metal interlocking mechanism --- making it the highest security bolt seal on the market. These seals are C-TPAT compliant and meet the new design and construction standards 10mm Thicker Steel Bolt and More Difficult to Tamper with- Unlike the majority of bolt seals (8mm steel bolt), is made of an all-metal high-strength steel construction. The clip - the actual locking mechanism - is embedded in a groove in the metal bush, making the seals stronger and more difficult to tamper with. Track & Trace Features- Unique correlative serial numbers with identical barcodes engraved (not painted) on both parts provide traceability and greater security as it prevent parts substitution or replacement. Anti-Spin Locking Mechanism- Anti-spin feature provides additional resistance to tampering by friction attacks.