Punching bag shopping mostly comes down to matching bag weight to body weight and being realistic about what proper mounting actually requires.
Bag weight should roughly correspond to body weight
A commonly used guideline suggests a bag weighing roughly half the user's body weight, which allows the bag to absorb impact and swing appropriately without moving so little that it feels rock-solid and jarring to hit, or so much that it swings unpredictably and becomes hard to work with rhythmically. A bag that's too light for a heavier or harder-hitting user swings excessively and becomes difficult to control combinations against; a bag that's too heavy for a lighter user can feel uncomfortably solid on impact and increase the risk of wrist or hand strain from an unyielding surface.
Hanging bags need genuinely secure ceiling mounting
Heavy bags, especially filled ones weighing 70-100+ pounds, need to be mounted to a structural ceiling joist or a specifically rated mounting point — not simply screwed into drywall, which cannot support that sustained weight plus the dynamic force of repeated striking. This is a real structural requirement, not an exaggerated caution, and it's worth confirming the actual ceiling structure can support a heavy bag, or opting for a freestanding base model instead, before assuming any ceiling location will work.
Freestanding vs. hanging bags
Hanging bags generally offer more realistic swing and rebound feel, closer to what's used in dedicated boxing gyms, but require secure overhead mounting and a fixed location. Freestanding bags use a heavy, often water- or sand-filled base for stability, requiring no ceiling mounting and allowing relocation, but tend to feel different underfoot and under impact than a properly hung bag, and can tip if hit with enough force relative to the base's weight and the bag's specific design.
Fill material affects feel and long-term durability
Bags filled with fabric or fiber tend to feel softer initially but can compact and harden unevenly over time with heavy use, requiring occasional redistribution of the filling. Water- or sand-filled freestanding bases add stability but can develop leaks or settle unevenly over years of use. Understanding that fill material genuinely changes over time with use, not just at initial purchase, is worth expecting rather than assuming a bag will feel identical years into regular use as it did new.
The one thing people forget
Wear appropriate hand wraps and gloves suited to the bag's firmness, rather than assuming bare-knuckle or minimal protection is fine for any level of use. Even a well-chosen, properly weighted bag can cause real hand, wrist, or knuckle injury with improper or absent hand protection, particularly with repeated, harder strikes over a real training session rather than occasional light use.