There are three main types and sizes of Sim card available, which fit specific devices. These are:
Standard Sim card (15mm x 25mm)
Micro Sim card (12mm x 15mm)
Nano Sim card (8.8m x 12.3mm)
When you order a Sim card from a provider, it'll usually send a 3-in-1 Sim, so if your phone supports a smaller size, you'll be able to break it down to the correct size for your phone. The latest smartphones will usually work with a nano Sim.