I have an older huffy MTB and it did not come with a chrome moly axle.
I bent 2 regular axles with the shift kit.
Regular axles are shiny metal, chrome moly axles are dark colored black looking.
It was inexpensive and well worth the $ 8 bucks or so.
You'll need to verify the axle diameter(mine was 3/8") and the length.
Longer than original is ok.
You'll need to use your own cones on the new ones.
Remove the old axle by undoing the nut and jam nut from the non-freewheel gear cluster side and slide the axle out.
If the bearings are the loose ball type, beware when removing the axle because they'll roll all over the floor making you say bad words.
Clean everything really well and pack axle grease into the "cups" inside the wheel.
The grease will hold the bearings in while you re insert the new axle.
I haven't had a bit of trouble since I replaced mine and it's been a good 400 miles or so.
By the way don't get discouraged, Niagara Cycles are slow shippers but I have ordered at least 6 things from them and they are good and cheap for everything having to do with bikes.
Here's the link to Niagara thru Amazon.com
http://www.amazon.com/Wheel-Master-Cro-Mo-Axle-Solid/dp/B000AO7HUW