# Interface Sets¶

In transition interface sampling and related methods, we need to define a set of interfaces for each sampling transition. In OPS, this is essentially just a list of volumes. However, it can be useful for that list to carry some addition information (such as the associated collective variable), so the InterfaceSet is a way to package that information.

For TIS, you will usually use the VolumeInterfaceSet or PeriodicVolumeInterfaceSet.

## Abstract classes¶

 InterfaceSet(volumes[, cv, lambdas, cv_max, …]) List of volumes representing a set of interfaces, plus metadata. GenericVolumeInterfaceSet(cv, minvals, …) Abstract class for InterfaceSets for CVRange-based volumes.

## Interface Sets for TIS¶

 VolumeInterfaceSet(cv, minvals, maxvals[, …]) InterfaceSet based on CVDefinedVolume. PeriodicVolumeInterfaceSet(cv, minvals, maxvals) InterfaceSet based on PeriodicCVDefinedVolume.