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SHARE BASED COMPENSATION - Restricted stock (Details) $ / shares in Units, ¥ in Thousands, $ in Thousands |  |  | 12 Months Ended
--- | --- | --- | ---
Nov. 22, 2018 $ / shares shares | May 18, 2015 shares | Dec. 31, 2020 USD ($) shares | Dec. 31, 2020 CNY (¥) shares | Dec. 31, 2019 CNY (¥) shares | Dec. 31, 2018 CNY (¥)
Restricted stock |  |  |  |  |  |
Shares converted (in shares) | 293,059 |  |  |  |  |
Exercise price (per share) | $ / shares | $ 0.4749 |  |  |  |  |
Share-based compensation expense |  |  | $ 145 | ¥ 947 | ¥ 1,624 | ¥ 8,121
Unrecognized share-based compensation expenses | ¥ |  |  |  | 1,666 | 2,720 |
General and administrative |  |  |  |  |  |
Restricted stock |  |  |  |  |  |
Share-based Compensation |  |  | $ 145 | ¥ 947 | ¥ 1,624 | ¥ 8,121
Restricted stock [Member] |  |  |  |  |  |
Restricted stock |  |  |  |  |  |
Issued (in shares) |  |  | (50,001) | (50,001) | (101,910) |
Shares converted (in shares) | 293,059 |  |  |  |  |
Exercise price (per share) | $ / shares | $ 0.4749 |  |  |  |  |
Restricted stock [Member] | Non-executive member of board |  |  |  |  |  |
Restricted stock |  |  |  |  |  |
Issued (in shares) |  |  | 0 | 0 | 47,743 |
Restricted stock [Member] | Employees |  |  |  |  |  |
Restricted stock |  |  |  |  |  |
Granted (in shares) |  | 510,000 |  |  |  |
Restricted stock [Member] | Employee and new hires |  |  |  |  |  |
Restricted stock |  |  |  |  |  |
Vesting percentage |  | 25.00% |  |  |  |
Vested (in shares) |  |  | 0 | 0 | 47,743 |
Restricted stock [Member] | Senior employee |  |  |  |  |  |
Restricted stock |  |  |  |  |  |
Granted (in shares) | 200,000 |  |  |  |  |
Vesting percentage | 25.00% |  |  |  |  |
Vested (in shares) |  |  | 50,001 | 50,001 | 54,167 |

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- Definition The number of equity-based payment instruments, excluding stock (or unit) options that are exercised during the reporting period. + References No definition available. + Details
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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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