Fits from 3 months to 2 years old with the snap buttons Adjustable 1 size for 3months - approx 2 years (10-12kg) depending on the child. Material: Waterproof PUL with elastic waist and thighs. Adjustable snap buttons so as to prevent poo leakage. Also Comes with inner mesh to hold "accidents" in the pool. Swim diaper is meant to contain fecal matter from contaminating pool water. Inserts are not necessary as it will only absorb water and make swim diaper unnecessarily heavier and uncomfortable to wear in water. This can also be used as a training pants.