Ⅰ. Rubber material
(traditional water-filled hot water bag)

Advantages
High temperature resistance, strong pressure resistance, not prone to cracking, long service life;
Large heat storage capacity, long insulation time;
High cost performance, low price;
Good sealing performance, no leakage.
Disadvantages
The material is relatively hard, poor fit, not suitable for hot compressing;
When filled with hot water in winter, it feels cold and hard;
Prone to aging and sticking, easy to crack after long use;
Heavy weight, not very portable.

II. PVC material
(affordable water-filled/charging heat therapy bag)

Advantages
The texture is soft, the feel is smooth, and the fit is better than rubber;
It is lightweight, portable and easy to store;
The price is low, and there are many styles;
It is highly malleable and can be made into irregular shapes.
Disadvantages
It is prone to bulge and age when exposed to high temperatures;
The heat retention time is average, and the heat dissipation is too fast;
Low-quality PVC has a plastic odor and is not durable;
The pressure resistance is weak, and it is prone to leakage.

III. Silicone Material
(Food Grade/ Medical Grade Heat Pad)

Advantages
Super soft and highly elastic, perfectly fitting the waist, abdomen, shoulders, neck, and joints;
Resistant to high and low temperatures, can be boiled and used for cold compress after refrigeration;
Non-toxic, odorless, antibacterial and easy to clean, does not mold or stick;
Anti-aging, with a much longer service life than rubber/PVC;
Explosion-proof and leak-proof, the highest safety level.
Disadvantages
The price is relatively high, the cost is higher than rubber and PVC;
The heat storage performance is slightly inferior to thick rubber, and the duration of heat preservation is slightly shorter;
Soft silicone is prone to flattening, and the pressure-bearing capacity is average.

Ⅴ.Diving material SBR composite material
(fabric sleeve integrated hot compress bag/belt style)

Advantages
The surface fabric is skin-friendly and non-irritating, and no additional cover is required;
It has good elasticity and a strap design, which can fix the waist, knees, and cervical vertebrae;
It has good heat insulation properties, continuously releases heat slowly, and is not prone to causing burns;
It is wear-resistant and resistant to pulling, suitable for sports therapy, daily therapy.
Disadvantages
The fabric is difficult to be thoroughly cleaned and is prone to accumulate dirt;
It is heavier than ordinary plastic models;
The price is slightly above average.

V. Felt/Cotton Filled Models
(Water Particle Heat Therapy Bags, Salt Bag Artemisia Bags)

Advantages
Skin-friendly and soft, maintaining a constant temperature and mildness, without causing skin irritation;
Microwaveable/electrically heatable, no need to fill with water, no water leakage;
Can add mugwort, sea salt, red beans, with therapeutic and health benefits;
Lightweight and portable, the shape fits the body curve.
Disadvantages
Shorter insulation time, fast heat dissipation;
Cannot be filled with water, only dry heat application;
The fabric is prone to getting dirty, not washable, and may become lumpy over time;
Improper heating may cause fire or charred smell.

Quick purchase advice:
Seeking durability and affordability, long-lasting insulation: Choose thick rubber
Seeking softness, affordability, casual use: Choose PVC
Seeking safety, no odor, close-body therapeutic use, cold and hot functions: Choose food-grade silicone
Seeking strap fixation, for joints/waist/shoulder use: Choose diving material SBR model
Seeking mildness, health benefits, no water injection: Choose salt bag/fragrant grass fiber particle models