Manual transfer switch device allows portable generator to safely feed power back to distribution board and home wiring. Prevents utility and generator power from being on at the same time. No putting electricians at risk and no damage to electrical equipment during power outages Electrical interlock kit is compatible with for QO or for Homeline 150 or 200 amp load center breaker panel boxes. Fits 1-3/8 inch spacing between main breaker and generator branch breaker, other same space panels may fit. Fits indoor/outdoor generators. Mounts in front of breaker panel, no additional control box or wiring required. Generator lockout kit easily switches utility power or connects generator to power all by sliding lock plate up and down to "lock position", clearly showing what you are running when protecting the generator. Keep away from darkness and cold during power outages. Built with high quality chemical resistant and thick solid aluminum alloy interlock switch plate, very for long-term use. Colour:Silver Material:Aluminum Package Contents: 1 set x generator interlocking parts Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.