Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: Better for your birds than concrete trimming perches

The bolts that hold it on are large, plastic bolts, with a diameter of about 3/4", which will keep it from being used in cages with short distances between cage bars. I make my own perch stands, so I had to buy a special thread grinder to be able to screw these new perches into Ziggy's portable perches. But my vet said to get rid of the concrete trimming perches. Obviously, I cannot report yet on the long term life of the product: in other words, after taking the perch off and cleaning it dozens of times, will the threads be as long-lasting as the metal threads on the concrete and other perches? But the perches are working well for the time being. Ziggy seems to like them.