HiMedia SD031-5CT (often referred to with the prefix HM-) corresponds to Streptomycin (S) antimicrobial susceptibility test discs. 

Product Specifications
According to technical documentation from HiMedia Laboratories:
Antibiotic Saturated: Each disc is impregnated with 10 mcg of Streptomycin.
Dimensions: The discs are made of high-quality filter paper with a 6 mm diameter.
Identification: For easy recognition, both sides of the disc are printed with the code "S 10".
Packaging: The "5CT" suffix indicates a pack containing 5 cartridges in a blister pack, with each cartridge typically holding 50 discs (totaling 250 discs).