These felt picks are made of synthetic felt.Do not make a percussive sound as the plastic and metal picks when you hit the strings.It is suitable for ukulele and guitar strings. The guitar picks is made of high-density felt material, it is firm and durable enough for your Ukulele and bass guitar, it will not mark or scratch your Ukulele. Can be use for Guitar,Bass, Ukulele, Mandolin, Banjo and other stringed instruments.