Difference between Gps311A / B / C model : 
A model is basic 
B model support engine cut 
C model support engine cut & remote controller & siren .

Function:  
1.Built-in gsm gps antenna 
2. Mini size 60X36X18mm,easy install
3. waterproof 
4. Realtime tracking by SMS /Web platform /Mobile app 
5. Alarms:
Low battery alarm 
Power off alarm
Geofence 
Movement alarm 
Over speed alarm 
Acc alarm 
6.Engine stop (for model B,C)  
7.SOS alarm (For model C only )       
8.ARM / DISARM by remote controller (For model C only)
9.Sleep mode to save power 
10.Gprs mode to save gprs data 
11.Balance checking

4 tracking solutions:
- SMS tracking by calling, return google map link
- Absolute street address by SMS
- free mobile app TrackerHome 
- free web platform 
      
Specifications:
DIM. 6.0×3.5×1.8cm
Weight 50g
Network GSM/GPRS
Band frequency 850/900/1800/1900Mhz
GPS sensitivity -165dBm
GPS accuracy 5m
GPS starttime
Cold status 45s
Warm status 35s
Hot status 1s
H version(High voltage version): 8V-80V
L version(Low voltage version): 8V-40V
Backup battery Chargeable 3.7V 180mAh Li-ionbattery
Storage Temp -40°Cto+85°C
Operation Temp. -20°Cto+65°C
Waterproof grade IP67

GPS311A package:Gps unit,3-pin harness,manual ,box 
GPS311B package:Gps unit,5-pin harness,relay,manual ,box
GPS311C package:Gps unit,5-pin harness,relay, remote controller ,manual ,box