Complex sentence: Bike parts are not easily broken (you cannot remove the seat), and they are not standard sizes, ie different parts will not fit bikes sold in case someone tries to disassemble parts to sell or use them for his personal bike.
Split into simpler sentences: Bike parts are not easily broken (you cannot remove the seat), and they are not standard sizes. For example, different parts will not fit bikes sold in case someone tries to disassemble parts to sell or use them for his personal bike.