Oh dear: Reading their 'About Us' page, linked below, it's evident that 'they' are NOT masters of English grammar. Ahem! So, much as their grammar is superior to the average Chinese English speaker, it's NOT professional quality. Therefore, I cannot recommend this application. If 'they' can't use it to provide them with perfect grammar, you aren't going to either. That's a shame as I was very enthusiastic to try this out.Examples of bad grammar on their 'About Us' web page:- 'We are a University of Cambridge spin-out, specializing in Artificial Intelligence and Natural Language Processing (NLP) technologies. [Remove the comma. Also, the developers may have an association with the University of Cambridge, UK, but they are NOT native speakers of English. That is clear.]- 'We are not a big team, at least not yet, but we want to deliver automated proofreading service differently:' [The correct word would be 'services'. The sentence is also incoherent with no connecting cause and effect.]- 'Frankly speaking, no grammar checker on the market previously is worth your money.' [This sentence has bad syntax. This is less confusing syntax: 'no grammar checker previously on the market is worth your money']- 'It is beyond our imagination that some grammar checkers only update once or twice a year.' [This sentence approaches incoherence. Replace 'that' with 'why'.]And so forth. Their grammar is better than 'ChingLish' but it's not proper English. Oh well.http://www.1checker.com/About/Companyinfo