Maple Leaf MR. Hop Up Rubber 80° for AEG

The Maple Leaf MR. Hop Up Rubber 80° for AEG has a wider and larger contact surface, making it easier to adjust the hop.

The number of degrees says something about the hardness of the rubber. 50 Degrees is the softest variety and 80 degrees the hardest variety. The different hardnesses can be used in different ways in your AEG.
It makes no sense to use the hardest bucking when it is around freezing point because the cold makes a bucking stiffer and therefore harder to adjust. It is precisely in cold temperatures that you want a softer bucking.

The hardness of the bucking is also linked to the weight of the bb you are playing with. You can easily use a 0.30gr bb on a 50 degree bucking but this will probably result in it needing to be replaced sooner than when using this weight on a 70 degree bucking.

In the end, it comes down to personal preference.