The Ryo Ryo no Mi is a Paramecia-type Devil Fruit that allows the user to increase weight of objects around them.
Strength and Weakness
The main strength of the fruit is the ability it gives the user to control the weight of things around in him. With a bit of focus, he can cause immense pressure to slowly crush them and slow them down significantly as if thousands of weights were strapped to their body. He can easily change the weight level as he sees fit to crush them further or lighten the load on them.
The gravitational power seems to be able to be overcome by brute strength, as Kedamono Jeran demonstrated the ability to break out from the crushing force by changing to his Heavy Point in order to free himself. The same standard Devil Fruit weakness applies.