excise duty on packing boxes for export

sir

i have a unit manufacturing packing boxes for exporters established in panipat city since long. i have not taken excise number yet. there are so many units also established in panipat but only few of them have taken exicse registration. my turnover upto 31.12.2010 is almost Rs. 300.00 lac. what is the basic exemption and wheather there is any other exemption if we supply goods to exporters only.