I have a Lowline Canopy, made of Steel frame and Colorbond skinned. BIG Doors on sides and Back. they normally fit fixed windows but I optioned them out because they let heat in as well as thieving bastards who want to knick your stuff! Easily resolved lighting problem with 3 "door" switches and some $1.50 LED strips. Its ROCK solid, doesn't require any internal Hoops to hold a roof rack and is secure as can be. It is riveted and welded, and after our 15000km odyssey on the Tanami, Gibb river road and cape Leveque, we lost 1 rivet. that's all. thee only dust is from when we open the doors.
If you are after sliding windows though.... i'm not sure. but its tough and well built. Back in 2007 when I got mine it was about $500 more than an ARB one if you included all the "extra's" ARB charged or like smooth finish, color coding (you need smooth finish if you want color-coding) and support bars for the roof Rack , and the extra to change sliding tiny windows into lift up tiny windows.
mine has no glass to break and no easy access for thieving cretins with a rock or a centre punch. not the cheapest, but pretty good value for money. And made by real Australians, in the Basin, Vic.