On a Cube electric bike, SL stands for Super Light, and refers to the aluminium used in construction. This means the e-bike will be particularly light, but it will also be very stable due to the high-tensile stiffness of the frame.
If you’re going to be transporting your bike, or even pushing it along when you need to dismount, a lightweight design is ideal—and it’s also perfect for smaller riders, which is why the CUBE Acid 240 Rookie Hybrid is an “SL” bike.
Other acronyms to look out for when choosing e-bikes include C:62: Carbon Fibre; C:68: Higher grade Carbon Fibre; and ARG: Aggressive Race Geometry.