Although strictly speaking there is no obligation to wear tzitzit when not wearing a four-cornered garment, today the custom is to undertake the obligation by wearing a specially designed four-cornered garment under your shirt all day, every day. Verses in the Torah explicitly state that looking at the tzitzit tassels reminds us to keep the mitzvot at all times and helps us overcome unseemly impulses. According to the Talmud (Menachos 43b), the commandment of tzitzit is the equivalent of all the mitzvahs combined.

When you set out to buy a tallit katan, you’ll have a number of issues to consider, including the fabric, the basic design and the type of tzitzit strings.

Choosing the fabric

According to halacha, wool is considered the fabric of choice, but cotton is also permitted. Both the Chazon Ish and the Vilna Gaon reportedly wore a tzitzit garment (known as “arba kanfot” or “tallit katan) made of cotton. Many Chassidim, who typically wear the tallit katan on top of their shirt, choose synthetic fabric because they do not wrinkle like cotton, but Rabbi Moshe Feinstein ruled that only woven fabrics – wool, cotton, linen, silk – are viewed as real garments according to halacha. He argues that in this regard synthetic fabrics that are not woven would be considered akin to leather, which is explicitly exempt from the obligation of tzitzits.

The design

Wool arba kanfot garments generally come with a black stripe near the front bottom edge, but sometimes you will find an option for white striping, which is the predominant Sephardic custom. Generally the neck opening has a slit running down the chest to make the tallit katan easier to don and wear, but some people insist on a round opening on the grounds that the minimum size is measured from the bottom of the slit, which would mean it does not meet the minimum size requirement of 18 inches (or according to more stringent rulings, 20, 22 or 24 inches respectively).

In recent years a new tallit katan design appeared on the market, known as NeaTzit or TrimTzit or “tzitzit shirt.” Generally made of cotton, it is partly closed on the sides to stay in place better, which is particularly helpful for kids or for adults playing sports. Some even wear it in place of an undershirt.

The tzitzits

Near each of the four corners is a hole (or a pair of holes according to the Chassidic custom). Be sure the eyelets are reinforced, otherwise the fabric will tear quickly whenever the tzitzits are pulled abruptly for whatever reason.

Cotton arba kanfot garments typically come with machine-spun tzitzit already tied. If you buy a wool tallit katan you may have an option of either machine-spun or hand-spun tzitzit strings. Hand-spun are clearly preferred according to halacha, and the difference in price is not significant. Occasionally you will come across very high grade tzitzits known as “lashonot” and “niputz lishmah,” and today many people opt for techelet, which is even more expensive and is a topic in its own rights.

Generally the tzitzit strings on a tallit katan are thin, but some people opt for the thick tzitzits generally reserved for a tallit gadol (a prayer shawl).

Whichever tzitzit strings you choose, be sure they are certified kosher by a reliable rabbinical supervisor (e.g. Eida Chareidit or Rabbi A.A. Wosner).

There may also be an option to tie them yourself, which is not very difficult to learn, and tzitzit tying guides can be readily found online.