Butler Creek

Measure the obj and eye sides (front and back) the eye pc is what you look into and the obj side is what you look out through!
Measure outside diam. Butler creek has a chart with inch to mm conversion and will tell you exactly what number you need!

Here ya go... measured with digital calipers.

Redfield Revolution 3x9x40

Objective = 46.7
Ocular = 39.69

Did you ever find the correct caps for your scope?

Hmmmm.... good question. I didn't buy them yet but looking at the chart on OpticsPlanet.com http://www.opticsplanet.com/butler-creek-flip-open-scope-covers.html I think these are the part numbers needed.

30270
30150

You might want to check with their customer service first before you make a purchase.

Your obj # 27
Your eye # 13

Is that confirmed with OpticsPlanet?

Their chart should have those numbers thos are BC's numbers according to your measurments in mm!
I have their conversion chart comes with the caps. I bought mine on eBay for 19$ for both.