I think they are more than adequate to support a 350 lb CB300F. But make sure you get Item# 65620
Stay away from the "low profile" paddock stand they make which is silver and made of aluminum. You need a Swingarm stand (black color) for this bike because the Cb300F does not have spools. So get Item# 65620 and bring your 20% off coupon that you will find on the internet at
https://www.hfqpdb.com/
The stands are good enough for a chap that just wants to do maintenance at home on his own bike. I wouldnt recommend it to a professional mechanic or a hobbyist that does extensive tinkering with multiple bikes. But to hold up the CB300F it is MORE THAN adequate. But still recommend a second human (even grandma) to hold the front wheel completely straight with the handlebars (to hold it steady while you lift the rear wheel with the stand and get it properly aligned).
Here is what may happen if you try to lift your moto by yourself on the stand:
And certainly dont "sit on the bike" while it is on the stand. Its good enough for working on YOUR BIKE