The unit of the resistance is Ohm, abbreviated, as Ω. The larger units, KΩ,  MΩ, GΩ are also used. 1KΩ=1000Ω, 1MΩ=1000KΩ, and 1GΩ=1000MΩ.

The resistance of a resistor is sometimes annotated as a 3-digit system. The first two digits represent a two-digit number, and the third digit is the number of zeros to be added after the two-digit number. But the three digits are not directly shown on the resistors, but are represented by three colored bands.

The color codes are:

Black: 0, Brown: 1, Red: 2, Orange: 3, Yellow: 4, Green: 5, Blue: 6, Violet: 7, Grey: 8, White: 9

The list of the resistors used in the Tube Mic DIY kit are:

Symbol	Value on the Schematics	Color Bands / Numbers on the Resistor
R1	10k	Brown, Black, Orange ( = 10 000Ω = 10KΩ)
R2	100K	Brown, Black, Yellow ( = 10 0000Ω = 100KΩ)
R3	270K	Red, Violet, Yellow ( = 27 0000Ω = 270KΩ)
R4	270K	Red, Violet, Yellow ( = 27 0000Ω = 270KΩ)
R5	22M	22M or 51M
R6	200M	200M
R7	3K	Orange, Black, Red ( = 30 00Ω = 3KΩ)
R9	22M	22M or 51M
R10	1G	1G or 1KM

The other important parameter for resistors is the power dissipation. Only R2 in the list is 2W, and the other are 1/4W. If you use a resistor with a small power value in the place where a larger power is required, the resistor will become too hot, and even be burned.