what are these 3

thanks everyone

Aftermarket brake controller, ISTR you need the adapter #3 for your brand of truck. Chev, Ford, or Dodge all different.

anon125 wrote:
"under dash trailer brake unit. "
what is that? we have been using the MH for 13 years towing our honda.
we have a 4 pin cable from the mH to car to make the honda brake lights work.
thanks all

we also use a evenbrake to stop the car when the MH stops.

Had to lookup what a "Evenbrake" was.

Your Evenbrake is a "wireless" brake controller which has a wireless "control head" that you put in your MH.

The one cable which someone mentioned is for connecting a WIRED brake controller into your MH wiring system.

KEEP that cable, in fact keep the 7 pin connector, then when you trade or sell the MH you can gift it to the next owner which might want to use it.

Might wish to UPGRADE your 4 pin connector to a 7 pin connector, this will add in BATTERY CHARGING to your "TOWED" vehicle..

Four pin connector does not charge your "towed" vehicle so your Evenbrake brake unit is always drawing down your "towed" vehicle battery..

If you are not able to DIY, you should not have to much issue finding a place to make that change. UHaul often will do that work.

"under dash trailer brake unit. "
what is that? we have been using the MH for 13 years towing our honda.
we have a 4 pin cable from the mH to car to make the honda brake lights work.
thanks all

we also use a evenbrake to stop the car when the MH stops.

Paying more attention to the labels on # 3 it's for wiring up an under dash trailer brake unit.

Not sure on the first, possibly a plug that was removed from a hole to run a wire.

second one is a standard 7 blade trailer plug

third is an adapter to connect under the dash and run either the trailer brake unit or a 4 pin connector in the rear which it sounds like you already have.

The 2nd one is a standard 7 conductor trailer plug.