Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the related assets and consist of the following (in thousands): | | | | | | | | | | At December 31, | | 2015 | | 2014 | | | | | Equipment (useful life 3 - 15 years) | $ | 2,864 |
| | $ | 1,289 |
| Tooling (useful life 2 - 5 years) | 851 |
| | 851 |
| Vehicles (useful life 5 years) | 39 |
| | — |
| Furniture and fixtures (useful life 5 years) | 104 |
| | 85 |
| Computer software (useful life 3 years) | 581 |
| | 378 |
| Leasehold improvements (the shorter of useful life or lease life) | 509 |
| | 509 |
| Construction in progress | 310 |
| | 18 |
| Property and equipment at cost | 5,258 |
| | 3,130 |
| Less: accumulated depreciation | (2,829 | ) | | (2,674 | ) | Property and equipment, net | $ | 2,429 |
| | $ | 456 |
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