The lead glass shower calorimeter consists of four stacks of TF1 leaded glass (similar to SF1). Each stack contains eleven blocks. The blocks are 10 cm by 10 cm by 70 cm and are read out at one end by a PMT.
To take the asymmetric flare of the SOS acceptance into account five of the eleven blocks are placed below the nominal central ray point of incidence, and six of the eleven blocks are placed above this point.
See the section on the HMS lead glass shower calorimeters for more information on the SOS lead glass shower calorimeters.