Recently we had a customer who told me he weighs 200 pounds and that standard 32 mm tefillin boxes “look silly” on him.
“Let me take a guess,” I wrote to him by email, “were your previous set of tefillin – the ones that were stolen from your car last week – Chabad tefillin?”
It turned out I was right. How did I know? Because Chabad likes to do things in a big way. Just as their mezuzahs are enormous, the tefillin they wear are also jumbo size, 40 mm x 40 mm. And they are much more expensive.
However, that is not to say that bigger tefillin are invariably more expensive. Some people want tiny tefillin, as small as 20 mm (e.g. Sephardim who want to wear both Rashi and Rabbenu Tam simultaneously), which cost a small fortune, and it’s very challenging to write such small parchments properly.
Years ago there were some tefillin makers in Eretz Yisrael that made 35 mm battim, but today that is very rare in tefillin peshutim, tefillin peshutim mehudarim, tefillin dakkot and tefillin dakkot ohr echad. In fact, tefillin dakkot ohr echad are even a bit smaller, at around 31 mm. Even tefillin gassot are usually 32-34 mm, although you can find a 35 mm set here and there.
One dealer I’ve closely familiar with sells Tefillin Peshutim Mehudarim in two sizes: 32 mm and 35 mm, but that size difference is generally not very significant.