These 3 heat sinks fit on any Raspberry Pi micro computer. They are easily to affix due to a layer of heat-conductive, double sided adhesive tape.
Just peel off the protective film, and press the heat sinks firmly and gently down on the chips.
Why using heat sink on Raspberry Pi?
Raspberry Pi microcomputer are designed to operate without heat sink. Therefore, the CPU clock speed will be lowered when the chip gets hot, cutting down on performance, to protect the processor. Processor and also other components on the board can overheat when the Pi is confined to one of those very popular little plastic enclosures.
These heat sinks help to keep the chip temperature closer to the environment temperature, which can definitely increase performance when the processor gets hot, and lifetime for the memory and other components.