Hmm this is strange, I can't reproduce the error as it doesn't turn red on my machine. What version of Grasshopper are you running, should be 0.9.0076, the latest version at the time of writing.Could you try to put a 'number' component in between the 'merge' component and the 'mass addition component'? Maybe it tries to add string values, which can't be done, so the number component converts the values into numbers before doing the mass addition.Another thing you should check is that your input values (the 0, 4.5 and 3) don't have an 'enter' or a white space after it. So go to the panel with the value and make sure that you have one line with only the "0", the "4.5" and the "3" respectively. This to prevent the values being read as strings instead of numbers or floats.Good luck and let me know if it worked out!Arie

thank you,.. it was somthing white or enter in the -->value 4.5. Now it works.