| Custom Engineering|
The duration of your Caltrops, Marked for Death, Spike Trap and Sentry is increased by 100%.
Increases the maximum number of active Sentries and Spike Traps to 3. Also allows Sentry and Spike Trap skills to hold 1 additional charge.
Custom Engineering is a Demon Hunter passive skill, unlocked at level 40.
For Caltrops, both the active and inactive duration is doubled.