Concentrations and credit risk (Tables)

12 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Net sales to customers

The net revenue representing at least 10% of total net revenue are as follows:

	Year Ended March 31,
	2018				2019				2020
	$ in thousands		%		$ in thousands		%		$ in thousands		%
Customer A		3,579		31		3,715		37		3,573		27
Customer C		1,599		14		1,225		12		1,239		9
Customer B		1,662		14		1,027		10		313		2
Customer D *		1,115		10		21		—		—		—
Customer E		1,050		9		996		10		—		—
		9,005		78		6,984		69		5,125		38

* That customer has stopped purchasing from us as of June 2017.

The following customers had balances of at least 10% of the total trade receivables at the respective balance sheet dates set forth below:

	March 31,
	2019				2020
	$ in thousands		%		$ in thousands		%
Customer C		136		23		241		30
Customer B		191		32		133		16
Customer A		127		21		99		12
Customer F		—		—		95		12
				76				70