SILCA Impero High Pressure Bicycle Frame Pump - Lightweight & Durable Bike Tire Inflator for Road & Mountain Bikes | Perfect for On-the-Go Cycling & Emergency Repairs

My old Masi is a 54cm frame. The top tube measures out to 20”. This was medium and a good secure fit. It feels solid and the machining is beautiful. Wish it came in colors but still is way better than expected. I got the sizing info from the Silca website.