I have an early Excaliber pre 3000 series number plus an FX2000..from what I can see the fill ports are the same. The valves, seals & springs are still available. My old FX2000 often leaked from the fill valve & now my RWS leaks. The only difference between the two is the stock & gauge. My understanding is the Webley Axsor is basically the same. I advertised them last year but changed my mind to have a go at doing the seals but never got around to it, might advertise again as it's a shame for them to gather dust.