I liked how fast the charge was Since I wear them every day from May to Nov and lasted 2 years and where still soft. Niente si è rotto subito Now the real test how do they sound???? I am seriously blown away at how good they are. she wears them probably twice weekly and plays in them in controlled environments, not outdoors. Zum Glück noch eine andere passende Schraube irgendwo gefunden. Less than 30 days it broke the side sole was loose The frequency response chart is not shown on Amazon, but I have scanned the image shown from the information in the box. November 13, 2020: Ive come to the conclusion I received a defective cartridge. Only fault, they are slightly expensive for bed slippers.