LNB holder to enable standard 40mm LNB's to be fitted to and is compatible with Sky MK4 Dishes, both zone 1 and zone 2. 
This holder directly replaces the 37mm version normally supplied with the dish. 
Now you can fit standard single, twin, quad, quattro and octo LNB's to existing MK4 dishes.

How do I know if my dish is a MK4?  
Simple- If the LNB holder fits over the arm it is a MK4, if it fits INSIDE the arm its not a MK4, and this holder will not fit.