DIYmall ESP8266 ESP-01S WiFi Serial Transceiver Module with 1MB Flash The PCB layout has changed for an improvement in WiFi radio performance 1MB Flash Memory Document link: https://nurdspace.nl/ESP8266, video link:https://youtu.be/mS2kQVD5Sxw What You Get: 1 X ESP8266-01S Module. Our 1 Year Warranty and Friendly Customer Service.