Instruct: Classify Amazon reviews into positive or negative sentiment
Query: great prop

these two pound toning balls are great props that can make some exercises more challenging and others easier. they are not too heavy and about right for either sex, although generally speaking (forgive me for stereotyping) some men will prefer the heavier three pounders and some women will opt for the one pounders. when you've learned an exercise without the toning balls, it can increase the challenge and strength. for roll ups, when you want a heavier counter-balance, the balls will reduce the challenge and give you hope.