These PWR Inserts work with barrels from Planet Eclipse and Inception Designs that are designed for PWR Inserts. They do not work with other insert barrel systems from other companies. The new system uses specially designed inserts that maintain all the easy ball entry features of the Stella barrel backs. This allows the use of a single outer barrel back that can be more cost effectively matched to the gun and it's anodizing yet maintains all Stella barrel performance features AND is available in many sizes. The design of these new PWR inserts is different to those you are previously familiar with. They are a very close tolerance to the barrel back, and yet can still be removed easily. The muzzle end has an external chamfer to promote the best alignment with the barrel front possible. They have an internal chamfer and radius ball entry lip, not a sharp edge, so are super gentle on the paint. They are marked with bore sizes that can be easily seen without removing the insert from the barrel back (and can also be identified by the colour as seen through the rearmost ports on our barrel front). The inserts are easily gripped and removed from the barrel back. We will have inserts immediately available in the following bore sizes (where marked from Inception) and Planet Eclipse will have bore sizes as shown below. We do have two other insert sizes in process to be released in the next few months.