What's in the box:

12V 125AMP Voltage Sensitive Relay VSR with Cable kit for 2nd Battery Double Battery Automatic Charging Relay Dual Smart Battery Isolator for ATV UTV (Standard)

VSR ( Voltage Sensitive Relay) are automatically controlled switches that allow two batteries to be combined when charging, and to be isolated when not charging. VSR helps to reserve a fully charged battery at all time, avoid the dead battery and possibility of towing on the sea. This Kit provides all the necessary cables, accessories and the VSR that you need to install the secondary battery with the VSR.

Features:
Automatically combines two batteries when charging and isolates the two batteries when not charging.
No voltage drops comparing to battery isolator diodes (0.6V).
Meets ISO8846 Ignition Protection, suitable for use in engine room.
Robust glass fiber reinforced nylon enclosure ensures long durability.
Built-in LED indication (ON when VSR engages).
Port for remote LED indicating VSR status (LED not included).
Surface or panel mount options provides flexibility when installing
Optional storage mode allows zero power consumption when engine is off.

Specifications:
Color: Black & Red
Nominal Voltage: DC 12V
Combine Voltage: DC 13.3V
Open Voltage: DC 12.8V
Continuous Rating: DC 125A
Intermittent Rating: DC 140A
Power Consumption: 10mA (Standby)
330mA(Engage)
0mA (Storage)
Terminal Studs: M6(1/4)
VSR Size: 6.9 * 6.9 * 5.7cm
Cable Length: 30cm,60cm
Package Size: 17.5 * 9.5 * 12cm
Package Weight: 692g

Package List:
1 x VSR (Voltage Sensitive Relay) with Mounting Screws
1 x 600mm (4 AWG) Red Cable Terminated at Both Ends
1 x 300mm(4 AWG) Black Earth Cable
1 x 300mm(4 AWG) Red Cable Terminated at Both Ends
3 x SC25-8 Copper Crimp Lugs (for cable)
2 x Red Battery Terminal Cover
2 x Black Battery Terminal Cover
1 x Instruction Manual