Moisture contents at which soil has the smallest plasticity is called limit.  

For determination purpose plastic limit is defined as the water content at which a soil will just begin to crumble when rolled into a thread of 3mm Dia.

Specification:-

Set of 6 moisture containers. 

Porcelain basin 150 mm Dia. 

Glass plate 20 cm x 15 cm having ground ends and one side frosted.

Brass or stainless steel rod 3 mm Dia x 150 mm long. 

Flexible Spatula. 

Plastic wash bottle 500ml.