It the last five years, constant reports of Iranian rocket deliveries to Hizbollah indicate that over 10,000 such missiles were brought into southern Lebanon. Most of these rockers are the smaller 107mm and 122mm models. The B-12 is a 107mm, 42 pound, 107mm, 33 inch long, Russian designed rocket that is very popular with terrorists. This rocket has a range of about six kilometers and three pounds of explosives in its warhead. Normally fired, from a launcher, in salvoes of dozens at a time, when used individually, it is more accurate the closer it is to the target. This 107mm design has been copied by many nations, and is very popular with guerillas and terrorists because of its small size and portability.
The 122mm BM-21s weigh 150 pounds and are nine feet long. These have 45 pound warheads, but not much better accuracy than the 107mm model. However, these larger rockets have a maximum range of 20 kilometers. Again, because they are unguided, they are only effective if fired in salvos, or at large targets (like cities, or large military bases or industrial complexes.)
It is believed that fewer than a hundred of the 240mm or 333mm rockets arrived in Lebanon. There may be more of intermediate caliber weapons (160mm), but little has been said about those. Thus it appears that the majority of Hizbollah rockets are the smaller ones. This is important because Hizbollah has to hide these rockets from constant Israeli aerial and satellite surveillance. Moreover, once hostilities begin (as they have now), it's going to be difficult to move large rockets around. Even the 122mm rockets are nine feet long, and not easy to conceal.
It's been no secret that, for years, Iran has been shipping, through Syria, thousands of unguided rockets to Hizbollah in Lebanon. As far back as 2001, there were reports of 240mm Fadjr rockets arriving in Hizbollah controlled territory in southern Lebanon. Both 240mm and 333mm Fadjr rockets are normally mounted on modified Mercedes-Benz 2624 15 ton trucks. There are either twelve 240mm (900 pound) rockets or four 333mm (one ton) rockets. About a third of the weight of rockets like this are the explosive charge in the warhead. The 240mm rocket has a range of 43 kilometers, the 333mm one, 75 kilometers. The Fadjr rockets brought into Lebanon are believed to have come individually, to be fired from locally built launchers. If enough care were taken in the construction of these launchers, the Fadjrs stood a good chance of hitting large urban areas within Israel.