The cage is safe for gliders - but it has a number of drawbacks that may cause you to hate the cage very quickly.
It is a flimsy cage - and it will rattle when ever your gliders jump around in it. It is held together by bent wires at each side.
The bottom of the cage is a structural part of the cage - and is not removable for cleaning - you will need to reach in through the cage doors to remove pieces of food that do not make it to the cage pan and to wash the cage bars.
The slide up cage doors are not large enough to allow you to put a glider safe wheel into the cage without taking part of the cage apart.
You may want to spend a little more and get a sturdy cage that has a metal frame work along the edge of each side and large doors that swing open for easy management of the cage. The Brisbane cage is a good choice for 2 or 3 gliders. If you want a larger cage the Madagascar or Congo cages are also great cages.
I have links to these cages on my web page along with links to several brands of Wheels made especially for Sugar Gliders.
http://www.gliderkids-diet.com/FAQ.html