how are they attached to the ladder?

4 bolts each. You will have to drill through the ladder. Use Red Loctite on the bolts when putting the nuts on. These are on all my extension ladders, and I won't go without!

Do you sell longer than 600c?

One size only. It's not for extending the ladder height is for leveling the ladder on safe ground. If you use it to extend the height all the time, you will eventually rip them from your ladder because of the angle.

Where are these manufactured? there is contradictory statements within descriptions, one states china and another usa.

Probably changes from time to time. IDK. I can tell you that I pained professionally for years and only used these on my 16' because it did not seem right to ask them to work heavy loads at extreme hights. They are super fast to implement and do not rely on a specific keyed hole with fixed increments. For stairs I had taken apart some 3/4" thick wooden shelves that were about 9" wide at a demo job and just connected 4 together so they could not come apart. These I used on a stair tread and this allowed my leg levelers to fit well short of maximum extension so there was more strength and I could easily work the stairs regardless of how thick the carpet might be. Or whether the stairs were wide and shallow or narrow and steep as per building code. These fully adjustable levelers made my life more efficient and effective for years allowing me to work otherwise dangerous situations on a completely even ladder. Love working with them. However, on the extreme high 28 or 32' ladders where the weight of the ladder and the leverage of added height come into play I would go with the wide levelers that force me to accept a keyed hole instead of infinitely adjustable for the added solidity. Love these levelers but did get one to bow slightly once when working at max extension carrying a 5er of paint with me. Stupid move on my part because I should have known better and worked more from the middle down and used support to raise the lower portion rather than making my leveler work too hard and likely out of spec. Continued to use it as it was intended for many years after. Major time saver and it sure does feel nice to make an uneven surface disappear mentally by working a level ladder up in the air no matter what the terrain.

Where can i buy replacement rubber feet?

Here on Amazon: https://smile.amazon.com/Ladder-Accessories-604-Replacement-Rubber/dp/B005V3N0TE Might be other options as well, check out similar items or what customers also purchased for amazons suggestions, often you find similar things to what you are looking at that way, or accessories to the item. Thats how I found the above link.

Material	steel
Brand	Xtenda-Leg
Product Dimensions	4.25"W x 21"H
Color	Orange, Silver
Special Feature	Anti-Slip
Item Weight	7.8 Pounds
Load Capacity	330.7 Pounds
Maximum Height	4.25 Inches
Manufacturer	Ladder Levelers Llc.
UPC	726097006007
Global Trade Identification Number	00726097006007
Part Number	600
Item Weight	7.8 pounds
Item model number	600C
Is Discontinued By Manufacturer	No
Item Package Quantity	1
Special Features	Anti-Slip
Batteries Included?	No
Batteries Required?	No

Ladder Leveler - Rubber Feet, Perfect for Extension Ladders, Stabilizer Attachments for Safe Use - Stable Platform for Uneven Ground - Easy Installation - OSHA Approved - 1 Pair

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