The main feature :
1. Built-in 2G/3G/4G industrial cellular module and sim card slot, insert SIM/UIM card to work directly.
2. Auto-dial feature, keep alive link
3. Built-in watch dog
4. 1 WAN RJ45 port + 4 LAN RJ45 port(WAN RJ45 can convert into LAN R45 to get 5 LAN RJ45 ports)
5. VPN (PPTP, L2TP, IPSec, GRE, Tunnel), SNMP
6. Standard SMA antenna can be replaced with high gain type
7. 1 DB9 port for DTU feature (Serial to Cellular Gateway feature,RS232 or RS485 option)
8. WiFi 802.11b/g/n 150Mbps (optional), can choose 300Mbps.
9. RJ45 WAN (xDSL) and Cellular backup each other (Route Fail Over Feature)
10. Two H820 can backup each other if one H820 line failed. (to be Dual sim dual module feature)
11. Always online, Reboot if the connection is failed.
12. WiFi can be used as WiFi client
13. Cellular, WAN RJ45 and WiFi Client can failover backup each other redundancy.
14. SMS/Voice call to control router to be online and offline (optional)
15. GPS (optional)
16. VRRP
17. RIP OSPF BGP (optional)
18. I/O port *2 (optional)
for the detail
http://www.e-lins.com/EN/3G_HSPA+_Router_List.html

Gprs SMS Router main features:

New Features of Industrial Dual Sim 4G Router on 4G Tech Update Full Review

Industrial brand LTE Wireless Module
Supports Packet Switched Data
100 Downlink, 50 Mbps Uplink
Wide Range Input voltage range from 5 to 32 VDC
5x10/100Mbps Ethernet Connectivity
3x Digital Inputs/Outputs... http://www.earthprex.com/industrial-dual-sim-4g-router-control/

Here we continue from where we stopped on the 4G LTE Tech Update as it is very nice that you should understand what you wish or need to Optaine before buying them... http://www.earthprex.com/industrial-dual-sim-4g-router-control/