I have an email in to Kensight asking if the Colt sight will fit or can be made to fit the GPs. In the mean time I dug out my feeler gauges and I can get a .011 in my 5 inch and a .009 in my 3 inch. Searching the interwebs to its deepest depths, I can only find the Bowen sights for a direct replacement and the go to fix for the stock sights is a shim. I am sitting here contemplating using the feelers for shim stock. Its raining here so it may become my rainy day project.