From Amazon
GARDENA Hose Clamp: Steel Hose Clamp to The Hose fixing, Clamping Range 25-40 mm (1 "), Width 9 mm, Screw Thread (7193-20)
Conrad Electronic
GARDENA Hose clamp 07193-20 Zinc-plated steel Bundle diameter (min.) 25 mm Bundle Ø (max.) 40 mm 2 pc(s)