3v3 Sustain for Raspberry Pi 4 $4.45 Pi4, ClusterHAT, FanSHIM, etc. NOT included. Keep the 3.3v rail alive between reboots. When rebooting a Raspberry Pi 4 the 3.3 volt rail is reset which causes problems for some HATs. 3v3 Sustain fits in between a Raspberry Pi and a HAT/pHAT and... Add to Cart