This is the part that goes between your pump and the start of your irrigation system. So-called "powered" because it includes a solenoid valve means you need a pump that's self-priming ie it's on standby but turns on automatically when the pressure drops - check out the DAB pump.

The kit includes:

Double ball valve - you shouldn't need this but for peace of mind, you can use this so you can perform maintenance on your irrigation system without fear the pump or solenoid valve accidentally turns on! 

Solenoid valve - the part you need to hook up to a controller of some sort like the Trolmaster NFS-2 + 24v control board, or the Grow Link

Filter - an essential part that keeps any crud from blocking your drippers 

Pressure Regulator - safety feature that ensures your drippers don't get blasted with 1000psi of pressure. Again, you shouldn't need to especially if you have a DAB pump where you can set the intended PSI output.

FloraFlex Male Adapter - this connects the kit to the 16/17mm tubing

You might see other websites with whip kits that include elbows - these are for the delivery line (aka trunk). However, we've not included them to give you the choice to add them on separately, as you may want to buy this to add/replace an existing whip kit.