Name the capacity for single cab size 2 medium tanker
CREATE TABLE "table1_2155350_2" (
  "category" text,
  "sub_category" text,
  "cab_size" text,
  "drive_wheels" text,
  "capacity_litres" text
);
SELECT "capacity_litres" FROM "table1_2155350_2" WHERE "cab_size"='Single' AND "category"='2 Medium tanker';