When linking prims together, the link-numbers assigned to them are done so in order of first selected, ranked last. This if you select a box, a cylinder then a sphere, your linked set will look like: 1 - Sphere 2 - Cylinder 3 - Box However, if you were to select a linked-set to include, then the behaviour is uncertain. For example, if instead of a sphere there was the following set: 1 - - - Torus 2 - - - Cone 3 - - - Pyramid Now we want to select first the box, then the cylinder, then lastly our new linked-set. The results we get will (usually) look like: 1 - - - Torus 2 - Cylinder 3 - Box 4 - - - Cone 5 - - - Pyramid This behaviour seems incorrect, as the linked set was selected first, the primitives comprising this linked set would be expected to have numbers assigned first, to look like: 1 - - - Torus 2 - - - Cone 3 - - - Pyramid 4 - Cylinder 5 - Box In this way, any linked-sets which are joined into larger linked-sets will retain the ordering of its linked numbers (though sets which get placed later will have these numbers increased), e.g the following example if the select went; linked-set, box, cylinder: 1 - Cylinder 2 - Box 3 - - - Torus 4 - - - Cone 5 - - - Pyramid This makes scripting things like llSetLinkAlpha and the newer llSetLinkPrimitiveParams a LOT easier as by simply linking the original object LAST when adding new primitives, it can be done without breaking a script which knows the link-numbers to affect. This behaviour will also be more beneficial should a hierarchical linking system ever be introduced