All information you need about MICRO SPLINE, HG L2 and HG Bodies

Shimano’s latest freehub technology innovations have introduced stronger, more dependable shifting systems and broader gear ranges across 12-speed road, mountain, and gravel groupsets. Each freehub system is engineered with unique features and compatibility options, designed to match the specific demands of various riding styles and individual preferences.

 

 

This brief overview highlights the differences between Shimano’s 12-speed MICRO SPLINE, HG L2, and HG freehub systems, helping you determine which one best matches your cassette and drivetrain requirements.

 

HG L2 Body

Intended Use:
Premium 2×12-speed road setups

Supported Cassettes:
12-speed Shimano DURA-ACE 9200 series

Cassette Range:
11T to 34T

Number of Effective Spline Teeth:
18

 

The HG L2 freehub represents the forefront of premium road cycling innovation, introduced alongside the state-of-the-art 12-speed DURA-ACE 9200 groupset. This advanced freehub was specifically developed to enable the use of aluminum in the construction of new DURA-ACE 12-speed cassettes, a material traditionally less common than titanium at this level—yet promising significant weight and cost advantages.

While aluminum is lighter and more economical than titanium for freehub applications, it is also more prone to wear and damage under high loads. Previous aluminum freehub designs often suffered from rapid pitting, caused by the concentrated pressure exerted on small contact surfaces between cogs and the freehub. The HG L2 system overcomes this challenge through its unique engineering: its smaller, deeper splines on both the freehub body and cassette cogs distribute forces more evenly, protecting the aluminum and preserving the advantages of reduced weight and cost.

 

 

The HG L2 freehub is exclusively compatible with Dura-Ace 12-speed road cassettes, which are suitable for both road and gravel groupsets. On the other hand, Dura-Ace 12-speed cassettes are backward compatible with standard HG freehubs, allowing them to be used with both 11-speed and 12-speed setups.

 

MICRO SPLINE Body

Purpose:
Optimized for 1×12-speed mountain bike and gravel configurations

Supported Cassettes:
Shimano 12-speed XTR, XT, SLX, and DEORE series

Cassette Range:
10T to 51T

Effective Spline Teeth Count:
23

 

Shimano’s MICRO SPLINE freehub technology made its debut alongside the 12-speed XTR mountain bike drivetrains in 2018 and has since become a hallmark feature across the brand’s top-tier mountain bike lineup. More recently, MICRO SPLINE has expanded its reach into the gravel segment, supporting Shimano’s 1×12-speed GRX gravel groupsets.

Designed to handle the broad gear ranges required by modern 1×12-speed systems, MICRO SPLINE enables the use of large-range cassettes, such as the 10-51T setup. The compact 10-tooth cog delivers the high speeds essential for competitive racing, while the massive 51-tooth cog ensures riders can maintain momentum and efficiency even on the steepest climbs.

 

Shimano’s GRX 1×12-speed groupsets are engineered for compatibility with mountain bike cassettes, ensuring a smooth integration with MICRO SPLINE freehubs. The unique spline configuration precisely aligns the shift ramps on each cassette cog, enabling HYPERGLIDE+ technology to deliver smooth, reliable, and uninterrupted shifts—both up and down the cassette range.

 

HG Body

Purpose:
Ideal for 11- and 12-speed road and gravel setups

Supported Cassettes:
Shimano road and gravel cassettes (11- or 12-speed)

Cassette Range:
11T to 46T

Effective Spline Teeth:
9

 

The HG freehub design stands out for its exceptional versatility, supporting the broadest selection of cassettes across Shimano’s road and gravel groupsets. With a proven track record spanning more than ten years, it offers compatibility with Shimano’s 12- and 11-speed road cassettes, as well as 11-speed mountain bike cassettes (note the spacer requirements below).

HG freehubs are engineered with precisely matched splines that ensure the cassette cogs engage smoothly and securely. This precise alignment also positions the cassette’s shift ramps optimally between cogs, enabling Shimano’s HYPERGLIDE+ technology to deliver crisp, reliable shifting—whether you’re moving up or down the cassette.

Note:
HG-800 and HG-700 road cassettes, along with 11-speed mountain bike cassettes, are fully compatible with HG freehubs, but require the use of a 1.85 mm spacer for proper installation.