Malchot Dovid Straps (Retzuot) are certified by the Badatz Beit Yosef and European Kosher Organization. Each Roll of straps comes with documentation of both letters of certification (Hechsherim).

Even if your Tefillin appear fine, internal issues can develop unnoticed. A recent case revealed how consistent moisture caused a subtle but invalidating warp in the Tefillin's shape. The Aruch HaShulchan mandates professional inspection every 3.5 years to prevent such problems.

תעשה ולא מן העשוי: Mezuzah must be right from the start. Fixes don't count. Intentionality matters.