Features: 
100% Brand new and high quality! 
Can provide for arduino libraries and routines 
Use DS3231SN precision clock chip， built 32.768 crystal 
Can provide precise year， month， day， hour， minute， second， in the morning and afternoon data 
You can output 1Hz signal， a second output signal 
You can use the CR1220 coin cell holding travel time 
The pull-up resistor R1 R2 own welding on the I2C bus 
Small size 3cm in diameter 
Pin spacing 22.86mm