Very handy assortment of plastic gears. These were made for tape drives and we have hundreds of different types that came to us in a mixture. Each is new and precision made. Each has a tiny 1mm to 2mm inner hole. We have no other information on these except that they are perfect for use in making tiny robots or experimenting with gears. Each assortment is slightly different and you will receive 12 gears (at least 6 different types maybe more in each package of 12). Assortments will vary slightly from picture shown as it is representative of an assortment.