Mei Tai

The seat width should encompass the base of your baby from one knee to the other. If the material reaches mid-thigh, the width should be increased slightly; if it reaches mid-calf, it should be narrowed slightly.
For example, you can place the mei tai on a flat surface (bed, changing table…), lay your baby on the apron and raise the waistband between their legs, to better assess the width to allow.

The top of the apron should reach the base of the neck. For an older child who wants to stick their arms out, it can stop at the shoulder blades, but no lower, to ensure the baby carrier remains safe.

A baby carrier scarf consists of a large rectangle of fabric cut into points at the ends; when used, the material is wrapped around oneself and the baby, then adjusted entirely according to one's comfort.
The mei-tai is a rectangular piece of fabric (apron) with four straps extending from its corners to form the waistband and shoulder straps. It requires fewer adjustments than a wrap carrier, and because the apron passes between the baby's legs, it's easier to secure it at the start.
The mei-tai remains enveloping and very comfortable and is perfectly suited to people wishing to rediscover cocooning sensations but not comfortable with a baby carrier scarf.

The mei-tai is a rectangular piece of fabric (apron) with four straps extending from its corners to form the waistband and shoulder straps. The waistband can be tied or clipped depending on the model, while the shoulder straps must always be tied.
On a pre-formed baby carrier, the belt must be clipped on, and the shoulder straps are sewn on and adjusted using pull straps.
The pre-formed carrier requires less handling, but it's also less enveloping than a mei-tai, which is therefore a bit more comfortable. Furthermore, with the mei-tai, the shoulder straps are crossed at the back of the wearer, which also improves comfort. However, it has the significant advantage of not dragging on the ground when being put on.