If you ever need to lock microwave frequencies or are uncertain about absolute frequency calibration then a GPS disciplined frequency reference is a must. Generally I find that the PCB design and RF shielding are better on products developed by RF savvy engineers (and on Tindie I find the products of a better technical standard). There is an added benefit in that the 3rd party software is available for control and output via a serial link for both Windows and Linux platforms. Really worth the outlay and patience over shipping. It's worth mentioning that on receipt check for any loose connections or nuts and bolts as the shipping process can shake things loose. So I am very pleased. Shipping times are affected by Covid at present so don't expect fast delivery until it over.