| In millions, except per share items | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| OPERATING ACTIVITIES | | | | | | | | |
| Net income (loss) | -15.6 | -22.3 | -16.6 | 10.0 | -4.9 | -14.1 | -12.2 | -1.3 |
| |
| Adjustments to reconcile net income (loss) to net cash flows from (used in) operating activities: | | | | | | | | |
| Depreciation and amortization | 1.2 | 0.9 | 0.7 | 0.5 | 0.2 | 1.1 | 1.0 | 0.9 |
| Stock-based compensation | 3.2 | 3.9 | 5.6 | 2.9 | 3.4 | 2.7 | 5.7 | 7.9 |
| Loss on disposal of fixed assets | 0.0 | 0.2 | | | | | | |
| Other | 0.2 | 0.1 | | | | | | |
| Change in operating assets and liabilities: | | | | | | | | |
| Accounts receivable, net | -1.0 | 0.9 | 0.9 | -1.9 | -1.2 | 0.1 | -0.6 | 1.2 |
| Inventory | 0.2 | 1.7 | -1.4 | -0.1 | 1.0 | 1.3 | -2.5 | -9.2 |
| Prepaid expenses and other | 1.0 | 3.0 | -3.0 | -0.8 | -0.4 | 0.1 | 0.1 | 1.2 |
| Accounts payable and accrued expenses | 1.6 | -2.1 | 1.6 | 1.3 | 1.8 | -0.4 | 0.5 | 0.4 |
| Net cash flows provided by (used in) operating activities | -7.5 | -7.3 | -2.2 | 12.6 | 3.6 | -2.1 | -4.2 | -6.7 |
| |
| FINANCING ACTIVITIES | | | | | | | | |
| Proceeds from issuance of convertible notes, net of issuance costs | 1.0 | | | | 0.8 | 2.0 | 1.5 | |
| Repayment of note payable | -0.8 | | -0.5 | -1.0 | -0.2 | -0.2 | 0.0 | |
| Net cash flows (used in) provided by financing activities | 4.4 | 3.3 | 0.0 | -1.2 | 0.1 | 1.7 | 4.2 | 8.2 |
| |
| Supplemental cash flow disclosure: | | | | | | | | |
| Interest paid | 0.0 | 0.0 | 0.1 | 0.1 | 0.0 | 0.0 | | |
| Supplemental disclosures of non-cash transactions: | | | | | | | | |