You have to be clear about the difference between a bashguard and a chainguard.
This link you provided: https://www.ebay.com/itm/SR-Suntour-...n724:rk:2:pf:0
Is not a bashguard. Bashguards are robust and designed to protect your outer chainring on rocky trails when your chainring would have hit a rock as you were going over an obstacle. The bashguard, being larger in diameter than the largest chainring absorbs the impact. The "bashguard" in that link is made of plastic and would shatter if you bottomed out going over a rock. That link shows a chainguard that is helpful in preventing a chain falling off the outside during a shift to the big chainring. These chainguards are not even all that useful in preventing trouser bottoms contacting the chain while pedalling since contact with the chain usually occurs during the pedal upstroke when the pedal is horizontal and your pant leg is well behind the "protection" of the chainguard