Concentrations and credit risk (Tables)

12 Months Ended

Mar. 31, 2016

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,
	2014				2015				2016
	$ in thousands		%		$ in thousands		%		$ in thousands		%
Sunbeam Products, Inc.		14,080		45		6,879		24		1,738		7
Fitbit, Inc.		10,396		33		10,593		37		14,145		59
Kern + Sohn GMBH		2,762		9		5,424		19		3,874		16
		27,238		87		22,896		80		19,757		82

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

	March 31,
	2015				2016
	$ in thousands		%		$ in thousands		%
Sunbeam Products, Inc.		101		8		87		10
Fitbit, Inc.		324		25		378		41
Kern + Sohn GMBH		224		17		204		22
Pitney Bowes Inc.		355		27		145		16
				77				89