The current racquet used by Murray is made out from the mold of "Microgel Prestige Pro 98", 16x19 string pattern with CAP grommet installed. Racquet stiffness has adjusted to Murray's preference.
Check out this thread for details:
You can see the string pattern and head shape of Murray's racquet is different from the retail Microgel Radical. Murray also adds quite a lot of lead under the CAP grommet to increase the racquet swingweight.