PSLV

                                           Generally all  Indians say "We are proud of ISRO".But ISRO say "We are proud of PSLV". What I mean to say is PSLV is  mainly responsible for present situation of ISRO.  From the establishment of ISRO, PSLV was launched 20 times. PSLV has a record 19 consecutive  successes. PSLV was a failure only on its maiden launch. To be very particular, Launch of PSLV is success only but it failed to place satellite in a correct orbit.
                                           PSLV is capable of launching 1600 kg satellites in 620 km sun-synchronous polar orbit and 1050 kg satellite in geo-synchronous transfer orbit.PSLV is a 45 m long, four stage launch vechicle. It has solid and liquid propulsion systems alternately. 
                                           India's most prestigious satellites CHANDRAYAAN, MEGHA TROPIQUES are placed in orbit by PSLV only. ISRO has a record of launching satellites more economically than any other country and the main reason is PSLV itself.
                                        You can watch internal structure of PSLV , Order of stages by cklicking on the link http://www.isro.org/scripts/pslv-flash.aspx.