Strike Industries lists that it does include a catch spring.
Correct, just the button is made out of billet aluminum.
No, it won't work for an AR-10. The Magazine Catch is typically not interchangeable with AR-15 parts due to the AR-10 design. Some exceptions apply but that generally requires a DPMS style AR-10.
Please email us at techsales@opticsplanet.com for further assistance.
Strike industries lists that it does include a catch spring.