Spectracide "Triple Strike" Weed Killer Questions

Have a gravel front yard with several trees and bushes.
Have a slew of weeds, and weed-grass poking thru the gravel.
Tried Roundup, and the weeds are pretty still healthy !
Anyone have any experience with this Spectracide/Bayer "Triple Strike" product ?
- Effectiveness, etc. ?
- Even more important, how safe is it for nearby trees (and bushes) ?
e.g., for any that seeps thru the gravel, do the tree and / or bush roots tend to absorb it ?
More "dangerous" to nearby 'good-stuff' than Roundup, e.g. ?
Thanks, Bob
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