For Aggressive Inline Skating. H-blocks are compatible with 60mm HD2, 72mm HD2, and FLT4 (Featherlite) frames by Ground Control. I couldn't find anywhere to buy the HBlock only, so I made my own. 

• Print in PLA+ or better (PA, Glass filled nylon, etc.)
• 100% infill (concentric or gyroid for strength). Alternatively, use a high number of walls.
• Ironing to smooth the groove (Recommended)

Also recommend baking these to ensuring proper layer adhesion. Initial tests showed some peeling at layers.

Requires 2 heat set brass inserts (M5)