M2M SIMs are available in every form factor, so it is easy to find one that fits your device design & the size and features you require.

Mini SIM (2FF): Mini SIMs are currently the largest removable SIM cards. Since the mid-1990s, this SIM has been in use. As of today, the Mini SIM has remained a great option for devices connected to the internet, such as cars and vending machines.

Micro SIM (3FF): A Micro SIM has a significantly smaller size than a Mini-SIM. It is large enough to facilitate physical SIM card swaps. Tablets and telehealth monitors are better suited for mid-sized IoT devices.

https://uktelecomdistribution.co.uk/m2m-sims-html.html is specially designed to be used in machines, with a range of tariffs and a quick and easy activation process.

Nano SIM (4FF): Nano SIMs are smaller and slimmer than the Mini and Micro SIMs. They are ideal for compact IoT devices, such as wearables. When a human is installing the device, the removable form factors 2FF, 3FF, and 4FF are good choices. The purpose of this is to assist with the initial booting of the device and SIM provisioning.

Embedded SIM (MFF2): Embedded SIMs (or eSIMs) provide better durability since the SIM is protected within the device. The latest MFF2 SIM cards often support eUICC remote provisioning. For many IoT deployments, especially those in rural areas or involving vehicles in motion, remote provisioning is beneficial. As an example, eUICC allows scooters to move from one city to another without requiring new SIM cards.