EF_BONEMERGE_FASTCULL
From Valve Developer Community
EF_BONEMERGE_FASTCULL is defined as 0x080, or 128.
This effect should be used with EF_BONEMERGE to make an entity inherit its parent's visibility.
Usage
To use this effect, including EF_BONEMERGE, turn off SmartEdit mode and add the following keyvalue pair to the entity: effects 129.
Note:If it is desired to use this with other effects, you should add the integer value of each effect to the value.Remember that you can set the effects value during runtime using an entity's AddOutput input with the input value effects x (x being any summation of effects flags to enable).
Warning:Using the AddOutput functionality for this, the new value may interfere with an entity's simulation functionality.