The perching is incidental; what these bird products are all about is foraging.
Coming in three sizes there are a few holes that go all the way through (mostly, unless you've come up with a super clever idea, you'll want these horizontal to the cage bottom) and a few holes that don't, so your food items will sit in a well.
You can use any perch for any parrot but obviously the small perch won't last very long for the big guys.
Now they're made of pine so they're super destructable (which is just another selling point if you ask us), but until it's beyond repair its simple enough to give it a scalding with hot water to clear out any nasties left behind after a fresh food forage. Just make sure to let it thoroughly dry (in sunlight gets you 5 stars in hygiene) before using again. You can purchase these with the stainless steel washers and wing nuts to attach it to the cage, but for those savy savers of spare parts you can save some cash and buy the perch without. All perches have stainless steel bolts to fit M6 wing nuts and any washers.
Small 20mm x 25cm. Holes are 10mm (3/8") in diameter.
Medium 35mm x 30cm. Holes are 16mm (5/8") in diameter.
Large 45mm x 35 cm. Holes are 19mm (3/4") in diameter.