The present invention relates to a drill string for percussive drilling comprising having a first elongate percussive drill rod comprising a main section and an externally threaded male end and a second elongate percussive drill rod comprising a main section and an internally threaded mounting sleeve. The male end and female ends overlap to form a coupling region and a thread clearance area is formed adjacent to the end most female thread. The mounting sleeve has a first region having a first outer skirt diameter, D1, at the axially rearward end and a second outer skirt diameter, D2, along part of the axial length between the axially rearward end and the main section forming a strengthened region wherein D2 is greater than D1.
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