All VideoRay models now use the same thruster cartridge seals, however older models may use different cartridge seals.
The current version has a slight blue tint to it. The older green cartridge seals have a smaller shaft seal diameter and will not fit on GTO thruster shafts or Pro 4 horizontal or vertical shafts. There is an older clear version that was used on Pro II era ROVs. The Pro II version has a different shape and is not compatible with current ROV models. The older cartridge needed to be removed in order to be inspected. The green and blue versions were improved so that these can be inspected in-place.