Plastic Bottles instead of Pea Gravel Pea gravel and pebbles can weigh down window boxes. Empty water bottles are a lightweight option. Place rinsed bottles inside the planter and add soil on top of them. The space between the bottles will allow proper drainage without the extra weight.
CD Technology 100-Pack White Paper Window Envelope Sleeves for CD Storage
#Accessories Premium Paper Sleeves #with Window & Flap. #Sleeve size approx. 5" x 5" plastic window is 4" in diameter.