Technical specs
| Microcontroller | ESP-8266EX |
| Operating Voltage | 3.3V |
| Digital I/O Pins | 11 |
| Analog Input Pins | 1(Max input: 3.2V) |
| Clock Speed | 80MHz/160MHz |
| Flash | 4M bytes |
| Length | 68.6mm |
| Width | 53.4mm |
| Weight | 25g |
More info here http://www.wemos.cc/Products/d1_r2.html