Buying a mezuzah case is not very complicated, but a few technical tips and aesthetics pointers will help.

How big?

Most mezuzah cases are designed to fit a mezuzah scroll that measures 6 cm, 7 cm, 10 cm, 12 cm or 15 cm. The two smallest sizes should be avoided, because it’s very hard for a scribe to write a kosher scroll in such small writing. And even if it is kosher, the writing is probably very low caliber, compared to what you can get for the same money in a medium size scroll (i.e. 10 cm or 12 cm). In recent years, especially in religious communities, the 15 cm size has been gaining in popularity. You can also find 20 cm mezuzahs, which are primarily for Chabad and synagogues.

Mezuzah case style, construction and materials

The look of your mezuzah case is up to you, depending on your own aesthetic preferences. But there is one key detail you have to keep in mind: If your doorpost is exposed to moisture, you definitely need a good seal. Many mezuzahs have a poor seal, and some have none at all, just a big opening on the back, with a piece of tape to keep the scroll in place. This means if you live in an apartment building, or you’re buying mezuzahs for interior doors, anything goes, but for the front and back doors of a house, you’ll want to take a good look at how the mezuzah is constructed.

Plastic might be the way to go. You can find super inexpensive plastic mezuzah covers for just a few dollars, and there are also many nice decorative ones. You’ll want it designed so that the scroll is inserted from the bottom, with a threaded bottom or a silicon cover. Also, take a look at the top to ensure it’s well sealed.

If your doorway is exposed to direct sunlight and high temperatures, avoid metal, sticking with plastic or wood. Also, transparent and translucent cases should be avoided.

Clear cases should also not be used for bedroom doorposts, because the scroll should not be visible where people sometimes undress.