Why do you need customization?

Harmonicas out of the box does not have a proper quality settings for the use of progressive techniques, such as overblow and overdraw. These techniques greatly enhance the instrument capabilities, transforming it from diatonic to chromatic instrument. Use three full octaves allows you to play any world music. To play overblow and overdraw notes reeds should be given the desired shape, and greatly enhance the instrument tightness.

That's what I do for this:

• Double-sided embossing - reducing the gap between the reeds and reedplates. Embossing is done on all sides of the reed. Near the rivets work is done with a scalpel. 
• Arcing - giving the optimal shape of reed along the slot.
• Gapping – adjusting the gap at the tip of the reed to reduce the air loss and give better response to bends.
• Grinding comb to impart maximum plane.
• Aligning plates for maximum contact with the comb. Polishing draw plate.
• Waxing to stabilize overbends on 6 - 10 holes.
• On harmonicas with steel reeds these are profiled to impart softness to bending notes. It also prolongs the service life of the reeds.
• Bend coverplates for improving seal between plates and coverplates.
• For extra playing comfort ground off sharp edges of reedplates. Harmonica sits comfortably in the mouth and does not rub the lips. 
• Harmonicas are tuned to compromise tuning suitable for playing chords and solo performance.  Also I can accommodate any desired minor or alternative tuning.
• After assembly harmonica is test-driven to fine tune the settings.
• Before shipment all harmonicas are complete disinfected.
• All work is carried out under a microscope for precise quality control.