Gassot Tefillin translate to mean Thick Phylacteries- quite a mouthful but just a reference to the thick strip of leather used to create these Tefillin. There are also inserts that make the Tefillin close smoothly. The Tefiilin are manufactured using repeated applications of several tons of pressure using an industrial press.
Tefillin Gassot are extremely durable due to the thick leather used to create them- in fact they typically last a lifetime. The thick leather means that they can also be repaired even when seriously damaged.
The straps of the Tefillin are made using the upper part of the hide (what is known in Hebrew as Retsu'ot Elyon) and the Batim of these Tefillin measure 34-35 mm.
The Tefillin are made in Israel by Pe'er HaSTaM and are certified as kosher having undergone a human and computer check. The Tefillin come with a certificate that proves that they were proofread and that they are Kosher.
Important to know:
If you are right-handed you wear the Tefillin on the left arm whereas if you are left-handed you wear the Tefillin on the right arm.