score:3
By air transport: up to 10000€ and not heavier than 50 kg. I think the engagement ring would pass these criteria.
The goods for private use except transport vehicles imported on customs territory of customs union in accompanied or unaccompanied luggage
- Goods for private use (except ethanol and the indivisible goods) transported by air transport:
customs cost of which does not exceed the sum equivalent of 10 000 euros and gross weight of which does not exceed 50 kgs
Source: Federal Customs Service of Russia.