Batim of this type are divided into two categories:
Simple mehudar Tefillin: In the batim of these Tefillin, the entire ketzizah of the bayit is made of a single hide. These Tefillin are fit from the outset (le-chatchilah), and therefore meet the stringent requirements that Oter Israel sets for all its products.
Simple Tefillin: These batim are made of many pieces of sheep leather that are glued to each other, without even a single piece of leather that unites them into a single unit, as in the type known as "Tefillin from a single piece of leather." The halakhic standing of such Tefillin is so low that some authorities entirely invalidate them. Accordingly, Oter Israel neither produces nor markets this type of Tefillin.