The Gates model 507C Sonic Tension Meter (product number 7420-0507) was recently replaced with the 508C Sonic Tension Meter (7420-0508). It is easy to identify the 508C model due to the green keypad, where the 507C model has a white keypad. The newer model works the same as the older model, and even uses the same attachments. The flat flexible sensor (7420-0205), inductive sensor (7420-0212), and cord sensor (7420-0206) will work with both Sonic Tension Meter models. The only two functional differences are the 508C does not have a low frequency filter, and the 508C has 40 data storage registers, where the 507C only has 20. Data storage registers are save slots that allow you to store mass, width, and span constants for specific applications. For more information about either model please click here.