Inventories (Details) (USD $) In Thousands, unless otherwise specified	Mar. 28, 2015	Dec. 27, 2014
Summary of inventories
Raw materials	$ 6,068us-gaap_InventoryRawMaterials	$ 6,329us-gaap_InventoryRawMaterials
Work in process	4,311us-gaap_InventoryWorkInProcess	3,979us-gaap_InventoryWorkInProcess
Finished goods	3,758us-gaap_InventoryFinishedGoods	4,433us-gaap_InventoryFinishedGoods
Provision for slow moving inventory	(656)us-gaap_InventoryValuationReserves	(643)us-gaap_InventoryValuationReserves
Total	$ 13,481us-gaap_InventoryNet	$ 14,098us-gaap_InventoryNet

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Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Amount before valuation and LIFO reserves of raw materials expected to be sold, or consumed within one year or operating cycle, if longer.

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Amount of valuation reserve for inventory.

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Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer.

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