I've had a GW-6900 for a few years now and decided to switch the band for a NATO. I accidently ordered two sets of the G2300B end part from Casio International and have now attached one set to the watch. The 24mm 'Zulu' NATO band ordered from natostrap.com fits nicely. The only criticism I have is that the end pieces are not the same colour as the actual watch. They're a bit more grey and a little 'sparkly'. So I decided to colour the extra set black using vinyl dye. After a few coats I think they came out nicely. A litte bit shinier than the watch but they're closer than they were before and hopefully they'll dull a bit over time.
Overall I'm happy with it; I haven't put the dyed ones on yet but I'll get around to it. It breathes a bit better, and is nice and thick not wimpy and thin like the original one :P