Just your standard snap fastener. Yes - you can get them from the fabric store, but not everyone is close to a fabric store. Although - I would never discourage anyone from the sublime experience of walking through aisles of fabric in hushed awe, stroking the velvet, marveling at the shimmery stuff, and reminding oneself that there are not an infinite number of hours in the day.
11mm By the pack of 10 sets.