Concentrations and credit risk (Tables)

12 Months Ended

Mar. 31, 2017

Accounting Policies [Abstract]

Net sales to customers

The net sales to customers representing at least 10% of net total sales are as follows:

	Year Ended March 31,
	2015				2016				2017
	$ in thousands		%		$ in thousands		%		$ in thousands		%
Fitbit, Inc.		10,593		37		14,145		59		8.472		48
Kern + Sohn GMBH		5,424		19		3,874		16		2,729		16
Pitney Bowes Inc.		2,476		8		1,969		8		2,435		14
Sunbeam Products, Inc.		6,879		24		1,738		7		1,563		9
		25,372		88		21,726		90		15,199		87

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,
	2016				2017
	$ in thousands		%		$ in thousands		%
Sunbeam Products, Inc.		87		10		162		14
Fitbit, Inc.		378		41		109		9
Kern + Sohn GMBH		204		22		328		28
Pitney Bowes Inc.		145		16		455		39
				89				90