Why we must make the bolt seals with 18mm pin and lock housing ?

Why we must make the bolt seals with 18mm  pin and lock housing ?

4.4 Evidence of tampering
4.4.1 Seals shall be designed and constructed so that tamper attempts create and leave evidence of that
tampering. More specifically, seals shall be designed and manufactured to prevent removal or undoing the
seal without breaking, or tampering without leaving clear visible evidence, or undetectable re-application of
seals designed for single use. Compliant seals shall demonstrate their ability to resist such tamper attempts
via the independent tests introduced in 4.4.4.
4.4.2 Seals constructed with plastic coating over metal components shall have sufficiently thick metal
components so as to preclude removal of the plastic coating, opening of the seal and re-closing of the seal
without leaving visual evidence of tampering.
4.4.3 To preclude the simple removal of a bolt seal by pulling the pin head or locking body through a worn
container hasp, the minimum diameter (or minimum widest cross-dimension) for the metal components of a
bolt seal shall be 18 mm.
NOTE The seal users who participated in the Working Group for this International Standard were from the
international liner shipping industry. They indicated that field personnel experienced recurring problems with 17 mm seals
which could be removed intact by pulling the pin head or locking body through worn container hasps. Those members of
the Working Group requested that ISO 17712 require an 18 mm minimum diameter for metal parts of bolt seals.
4.4.3.1 The 18 mm minimum shall become effective 18 months after the publication of this International
Standard as described in Clause B.2.
NOTE 1 An 18 mm minimum will require engineering, materials and manufacturing changes for most bolt seals.
Assuring a smooth, cost-effective and fair transition will require explicit time-phasing and user education. Annex B
specifies the bolt seal minimum diameter adoption/obsolescence process.
NOTE 2 In order to reduce the risk of inventory imbalances, seal manufacturers, distributors and users are encouraged
to consider the adoption/obsolescence provisions before initiating large production runs or purchases of <18 mm seals.
ISO 17712:2010(E)
6 © ISO 2010 – All rights reserved
4.4.3.2 Until the 18 mm minimum diameter becomes effective, seals shall be designed and constructed
so as not to permit removal without breaking. Once the 18 mm minimum diameter has become effective, all
bolt seals shall meet this requirement in order to be ISO 17712 compliant.