Part of the Castelli Race bags range, the Undersaddle Mini is the perfect bag for sticking on your road bike to carry some summer essentials.
Super compact this fit and forget under saddle, seat-pack can be crammed with a couple of (road) inner tubes 18-25mm a multi-tool, a spare link and a few £10s. In short most of the things you might require on a ride. It fits with a single strap (through the rails no need for a seatpost stabiliser), this strap uses a magic moulded hook and loop fastener that can be trimmed at home and that won't fur your shorts. The Mini bag is also weather resistant as is the zip. It's not totally waterproof but its better than most. The zip pull sits in a little cave so it stays silent and doesn't open mid-ride. The rear wordmark is reflective and the lining is in a pimp corporate red. Could you ask for more?
Possibly the greatest accolade for the Castelli Undersaddle Mini is you forget its there.
Features:

• Water and stain resistant materials
• Water-resistant zipper
• Water resistant construction
• Adjustable hook and loop attachment strap
• Internal storage pocket
• Reflective accents
• External dimensions 5 x 5 x 13cm (enough room for a Silca Italian Army Knife Tredici Bike Multi Tool or similar 2 road bike inner tubes a spare link and some folding cash).

Please Note This is water resistant not waterproof. If you ride in heavy rain with no mudguards water will eventually get into the bag, so put everything in a plastic zippy bag just in case