433Mhz receiver and transmitter
This receiver and transmitter were selected because they don't require you to solder on an antenna.
To save yourself $4 you can buy a much cheaper alternative receiver which works better (because it's shielded), but requires you to attach the antenna yourself. You will also have to grab a transmitter from any other cheap kit.
Do not buy the 'LORA' version by mistake, it looks very similar.