These 2-hole slot pop bottle waterers SCREW ON bottles! The springs come with hooks on the end to make it easier to get on & off the cage. Very sturdy. 
 
Each screw-on pop comes with 1 spring with hooks.
 
Available in purple, green, or red.
 
Only sold individually
 
Add the screw-on bottle with lid: 16oz Plastic Bottle for Pop Bottle Waters