It this product safe?

[Campbell]

I need a heater for my 5 gallon tank, and I like the 'look' of this one. It says it can go under the gravel, but is this safe and effective? Also if you would recommend any other heaters that would be great.



Product Description:
7.5 Watt Mini heater for 2-5 gallon aquariums is completely submersible and can be easily hidden underneath gravel to keep your fish and decor in the lime-light, not your equipment.
Recommended for: 2-5 gallon tanks
Increases temperature*: approx. 5° F (2 gal)/4° F (5 gal)

[Fishin Pole]

I cant really respond or comment on this certain heater, but i have 7 tanks running right now and 6 of them, i'm using Hydor heaters on.......I think they make a very nice, reliable product.........