Another rollergun type is the "Fusion" which is a hybrid of the other rollergun types and is distinguished by having a short set of bands which remain on the gun’s top deck and which are connected to the end of the drive cables that wrap the muzzle rollers. That means the bands do not travel around the muzzle rollers at any time, most of the propulsion being derived from the bands on the bottom deck. If the bands top and bottom are the same rubber type and size then the upper set don’t have to be stretch limited, but if the lower bands are thicker or in multiple sets with a bifurcated connection to the drive cable then the top bands need an inner cord to stop them being over stretched. Being stretch limited they add nothing to cocked gun cable tension until the spear is released at which time the top band set can start to contract. The diagram below compares a standard rollergun (if there is such a thing) to the simplest form of a Fusion rollergun.