AMMO by MIG Accessories Flexible Masking Tape (1mm x 55M)

From the Manufacturer:

This tape is perfect for airbrushing as it prevents paint from seeping through when used properly. The flexible material will allow you to mask any kind of contour including curves and rounded shapes, obtaining a uniform result when painting completely unrealistic sharp angles. This tape leaves no trace on any surface and will not damage the base paint. This masking tape can be easily cut with scissors or directly on the model by delicately using a fine tipped blade.