Q.Why are the characters such as "4R7" or "100" printed on some products?
Inductors (Coils) > Inductors (Coils) > Inductors (Coils)
These are the inductances expressed in a unit of microhenry (uH).
The first two digits indicate significant figures and the third digit a multiplier. When there is an "R", it indicates a decimal point, and all numbers are significant figures.
R47 = 0.47 /uH
100 = 10 x 100 =10 /uH
101 = 10 x 101 =100 / uH