GRAVEL STABILISATION GRIDS FOR PATHWAYS Nidagravel 129 Honeycomb Gravel Stabilisation System Our Nidagravel 129 gravel trays hold gravel in place permanently within honeycomb cells in a handy small format sheet size. Nidagravel 129 gravel retention grids are the smallest size gravel grids in our range, making them ideal for small to medium projects and DIY installation.