VRM (Voltage Regulator Module) on the HD4870 and HD 4890 cards tend to get quite hot during operation. Thermalright has decided to form special coolers to cool down these parts of the video card. Called the VRM R1 and VRM R2, they work together with the HR-03 Rev.A, HR-03 GT, GT V2, T-Rad2, and T-Rad2 GTX coolers. They measure 122×106x100.25 (LxWxH) mm and 133×53x120 mm respectively. The cooler consists of a copper heatsink connected to an aluminum fin block through two nickel plated copper heatpipes. The aluminum fin block allows you to latch on a 80mm fan. Both the coolers weight 160 grams each and differ only in the orientation of the aluminum fin array.

Source: TechConnect Magazine