In a vernier callipers, \( 50 \) vernier scale divisions are equal to \( 48 \) main scale divisions. If one main scale division \( = 0.05 \, \text{mm} \), then the least count of the vernier callipers is ____________ \( \text{mm} \).
\( 0.05 \)
\( 0.02 \)
\( 0.005 \)
\( 0.002 \)