The quality of papers published in the Metrology and Measurement Systems journal depends to a large extent on the quality of peer review process that, being an integral part of scientific publishing procedure, confirms the validity of accepted manuscripts. Our Reviewers are experts who volunteer their time and knowledge to support Authors in improving their manuscripts. This is an important and responsible activity in which they should be guided by the best intentions while taking into account a number of key aspects of evaluation. The Peer Reviewer is primarily responsible for critical reading of a manuscript and then providing substantive, constructive, and honest evaluating feedback to Editors and Authors about reviewed submission. This evaluation should: (1) result from a balanced and impartial consideration of the strengths and weaknesses of the manuscript, (2) show ways to eliminate weaknesses and improve the strength and quality of the work, and (3) assess the originality and potential of the described solution in relation to the state of the art and development trends. Developing a valuable review is then a non-trivial task and depends on meeting several basic conditions. Therefore, before reviewing the manuscript, a Reviewer should consider at least the following three issues. 1) The Reviewer is asked to consider if the manuscript he is being asked to review match his expertise. If a topic of the manuscript does not sufficiently match his area of expertise, he should rather promptly notify the editor and, if possible, recommend alternate reviewer(s). 2) The Reviewer should assess his ability for timely preparation of review. Typically, the review of a manuscript should be completed within three weeks. If, for any reasons, this time frame may not be met please let the editor know and, if possible, suggest an alternate reviewer(s). 3) The Reviewer should also consider any potential conflicts of interests resulting from competitive, collaborative, or other relationships or connections with any of the authors, companies, or institutions connected to the manuscript. It is important to disclose all such conflicts to editors before reviewing. If you have any questions about potential conflicts of interests, please do not hesitate to contact the editorial office. When reviewing a manuscript, the Reviewer is asked to express his opinion in four general parts of review concerning (1) Synthetic evaluation, (2) Confidential information for Editors, (3) Information for Authors, and (4) Reviewer decision. In the first part of review, i.e. Synthetic evaluation, the Reviewer answers briefly (YES/NO) for specific questions regarding the content of the manuscript. For example, whether the subject fit to the profile and scope of the journal, or whether the contribution described is significant and original enough, or whether the title and abstract are adequate to the contents, and so on. A set of detailed questions appears at the beginning of paper evaluation in our Internet Editorial System. In the second and third parts of review, i.e. Confidential information for Editors and Information for Authors, we expect all reviewer comments that, respectively, help Editors to make a decision on the manuscript and help Authors to improve their paper. Comments should be constructive and designed to enhance the manuscript. Reviewers are asked to make their comments as complete and detailed as possible and to express their opinions clearly using arguments and references if necessary. Specific comments that cite text line, figure or table numbers are most helpful. Preparing his comments the Reviewer is asked to take into account the following aspects. 1) The quality and originality of the manuscript content. First of all the Reviewer should assess if the manuscript content is sufficiently novel and interesting for readers to justify publication. It should add important contribution to the canon of knowledge while the paper itself should adhere to the journal’s standards. To determine the content originality the Reviewer might wish to do a quick literature search using scientific databases such as Web of Science or Scopus. If the research has been reported previously, pass on references of those works to the Editor. 2) The arrangement and clarity of the manuscript. The Reviewer should evaluate consecutively each part of the manuscript. Assessing the Introduction he should rate whether the presented ideas and solutions are described accurately, and whether the introduction clearly states the considered problem. The Introduction should summarize conducted research to provide context and explain how the current state of knowledge were developed or improved by the Authors. The next part of the manuscript should typically contain description of the proposed solution, i.e. a Method or/and Technique, which is new or overcomes existing limitations. The Reviewer’s task is to assess whether the solution is really innovative and why it is better than existing ones. Please support your general remarks, positive or negative, with concrete evidence. Please also comment on any possible research or publication misconduct, such as the manuscript reports data or conclusions already published (or in press), or the Authors plagiarised another publication (someone else’s or own). It is also important to evaluate if the solution is described sufficiently accurately and explained in detail. This part of the manuscript should allow the reader to replicate the research. In the next part of the manuscript, regarding Tests and Results, a test setup, performed investigations and obtained results should be described. This is also the place where the Authors explain what they discovered during their research. The Reviewer should consider if this issue was clearly laid out and if the appropriate analysis was conducted. The manuscript should also make it clear what type of data was recorded and with what precision it was measured/collected. However, an interpretation of obtained results should be included in the next section, i.e. Conclusion or Summary. The Reviewer should consider if the claims in this section are supported by the achieved results and if they seem reasonable. The Authors should indicate here how the results relate to assumptions or expectations, and to earlier research. The conclusion should also explain how the performed and described research has moved the scientific knowledge forward. The last important part of the manuscript contains References. The Reviewer should assess if they are adequate, as up to date as possible, and belong, at least some of them, to broadly understood metrology. Please, do not be afraid to suggest the Authors references that are missing or seem necessary for the paper, especially from journals the most important for the field of metrological methods and technology. The example journals are listed here (link). 3) The manuscript formatting assessment. The Reviewer is also responsible for evaluating if Figures and Tables included in all parts of the manuscript are appropriate. Especially, whether they properly show the data and are easy enough to interpret and understand. The Reviewer should consider if the length of the manuscript is relative to the content and fulfills journal requirements. He should suggest, if needed, that certain portions of the manuscript should be expanded, condensed, combined, modified or deleted. The manuscript has to comply with the Author guidelines. It is also highly appreciated if the review of manuscript, especially concerning article that was not written by a native speaker, contains comments leading to English quality improvement. If the reviewed manuscript is exceptionally good and makes a significant contribution to the existing literature, please do not be afraid to write it. Please remember! The Reviewer should respect the confidentiality of the manuscript, then he should not reveal unpublished manuscript content or use the obtained information in his own work. In addition, the content of his review and his recommendation should also be considered confidential. To remain anonymous, he should avoid comments to the Authors that can serve as tips to reveal his identity.