Bicycle rear sprocket assembly

A bicycle rear sprocket assembly comprising:

• at least one sprocket including a plurality of internal spline teeth configured to engage with a bicycle hub assembly, at least two internal spline teeth of the plurality of internal spline teeth being circumferentially arranged at a first internal pitch angle with respect to a rotational center axis of the bicycle rear sprocket assembly, the first internal pitch angle ranging from 10 degrees to 20 degrees, the plurality of internal spline teeth having an internal-spline major diameter;
• and
• an internal cavity having a maximum outer diameter larger than the internal-spline major diameter,
• the at least two internal spline teeth including a plurality of internal-spline driving surfaces to transmit a driving rotational force to the bicycle hub assembly during pedaling,
• the plurality of internal-spline driving surfaces each including
• a radially outermost edge,
• a radially innermost edge, and
• a radial length defined from the radially outermost edge to the radially innermost edge,
• a total of the radial lengths of the plurality of internal-spline driving surfaces being equal to or larger than 7 mm,
• the internal-spline driving surface having a first internal-spline-surface angle defined between the internal-spline driving surface and a radial line extending from the rotational center axis, the first internal-spline-surface angle ranging from 0 degree to 6 degrees,
• one tooth of the plurality of internal spline teeth has a first circumferential spline size,
• other teeth of the plurality of internal spline teeth each have a second circumferential spline size that is smaller than the first circumferential spline size,
• a total number of the other teeth of the plurality of external spline teeth being equal to or larger than nine,.
• one space circumferentially adjacent to the one tooth of the plurality of internal spline teeth has a first circumferential space size, and
• other spaces circumferentially adjacent to the other teeth of the plurality of internal spline teeth each have a second circumferential space size that is smaller than the first circumferential space size.