I had always been under the impression that the only thing you have to look out for when buying a kosher tallit katan is the tzitzit. Many people insist on hand-spun tzitzit rather than machine-spun tzitzit, but the garment is just a garment – or so I had always assumed. Of course in the case of an adult you have to make sure the tallit katan meets the minimum size requirement according to halacha, but as long as the garment has holes in all four corners, what could go wrong?
Tallit Katan: Wrong Head Space
Recently I discovered that a lot can go wrong. First of all, you may think your tallit katan meets the minimum size requirement because it’s long enough and wide enough, but if the head opening is too big, you may be in for an unpleasant surprise. According to halacha, if the open space is less than the cloth, we don’t take it into account, but in many cases the shoulder straps are made too narrow.
Picture a tallit katan laid flat on the table. If each shoulder strap is 10 inches wide and the open space is 9 inches wide, then the tallit katan is kosher. (This is known as rubo.) In the case of children’s sizes, you will almost never come across rubo, but in the larger sizes tallit katan manufacturers should ensure the opening is not too large, yet in many cases, they don’t.
Another issue is the placement of the holes in each corner. They should be located between 4 and 5.8 cm from the edge, but again, many tallit katan makers are not careful to adhere to the halacha in this regard.
Wool Versus Cotton
These problems are much less common in the case of wool tallit katans, but if you are buying cotton, be aware of the issues.
I have found a very upstanding tallit katan maker that insists on all these details, and G-d willing I am phasing out my the larger size tallit katans in cotton that I normally sell, in favor of this product.