Thought I'd show off the connection between normal Lego system, Duplo, and Quatro : r/lego
Quatro | Brickset: LEGO set guide and database
Lego Duplo Quatro Red 2x4 Brick Parts x3 | eBay
5470 My First QUATRO Figure - Brickipedia, the LEGO Wiki
LEGO 5357 Large Quatro Bucket | BrickEconomy
Lego Duplo Quatro 5357 83pc w/bucket and Lid Large-Sized Bricks 673419042222 | eBay
thebrickconsultant on Twitter: "Found some LEGO Quatro in the charity shop today. LEGO x2 = Duplo x2 = Quatro! And they all fit together 🙂 Shame the storage boxes are not a
Lego Duplo Quatro 5357 Bucket 75 Pieces Large-Sized Bricks 1-3 years Old VGC 673419042222 | eBay
LEGO Quatro: Large Quatro Bucket (5357) for sale online | eBay
LEGO QUATRO: Medium Quatro Bucket (5356) online kaufen | eBay
history - Giant LEGOs--that aren't QUATROs? - Bricks