Topeak Wedge Drybag with Strap Mount (Medium)

Size: Medium - 6.9” x 4.5” x 4.3" inch
Protect your gear while riding in wet, nasty conditions
MATERIAL - 210 denier / 420 denier nylon waterproof fabric sonically welded seams, Constructed from a tough, sonically welded and seam sealed waterproof material
CAPACITY - 1 L / 61 ci (Medium)

ATTACHMENT - Nylon straps / Buckle, Mounts with our innovative Quick Release Buckle system to fit all railed saddles

INSULATION - Semi-rigid EVA foam
SEAT POST DIAMETER - Fits ø25.4 - ø34.9 mm
ADDED FEATURES - Safety light clip, Reflective printing
WEIGHT - 170 g / 5.98 oz (Medium)
SIZE - 18.5 x 11.5 x 11 cm / 6.9” x 4.5” x 4.3” (Medium)

https://www.topeak.com/global/en/products/197-Waterproof-Bags/329-WEDGE-DRYBAG