Mishnah Berurah — משנה ברורה

Of a child etc. - This is a child that is 9 years old. In the Responsum of the Rem"a, siman 110, he questions how do people go out with a four cornered garment (ie. their טלית קטן) that is smaller than this. And the essence/summary of his words are that it is permitted to go out with them [for it is] better than to go the whole day without ציצית [at all]. And in Darchei Moshe, siman 9, he wrote that the people should be taught that they should recite the blessing in the morning on their טלית גדול and [have in mind] to exempt their טלית קטן and then they may go out with it all day. But nevertheless, if it's possible for a person to make it (ie. the טלית קטן) large enough so that it's the [minimum] measurement, "how good and how pleasant it is" - Until here are his words (ie. from the Darchei Moshe). And one should make the [material that passes over the] shoulders wide so that it's recognizable and be considered a garment and not [just] straps.