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This wire guide is from a European competitor the poor inside finish is the result of their use of the “DOM process” (drawn over mandrel). Most tube manufacturers cannot effectively draw over mandrel under 1mm or .040”   This means that in order to reduce the tubing further, a process called “sink forming” is employed.  In sink forming, the outside diameter is reduced by drawing it through a die, causing the inside diameter to collapse proportionately

The three guides shown here all have an inside diameter of approximately .021” or .5mm

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From a US competitor. Here, again, we see evidence of draw lines.
Although the ID surface appears better, tube steel is often inconsistent and may require drill reaming or intense lapping to remove draw marks.

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