def depth_breaks(increment_mm, max_mm):
    """Return a list of tuples representing depth ranges from a given depth increament (mm) and the maximum depth required"""
    dd, dmax = increment_mm, max_mm
    a = [i for i in range(0, dmax, dd)]
    b = [(a[n], a[n+1]) for n, i in enumerate(a) if i != max(a)]
    return(b)