We have a set of 33 prayer beads in our collection.
Prayer beads are referred to as "Misbaha", "Tasbih" or "Sibha". They commonly have 99 normal-sized beads, (corresponding to the Names of God in Islam), with two smaller or mini beads separating every 33 beads.
Sometimes only 33 beads are used, and the person praying would cycle through them three times. The beads are traditionally used to keep count while saying the prayer.
They are widely used today in Sunni and Shia Islam, but not in all sects of Islam.