What size?

[200xth]

Usually it is determined by the 15 -20% rule. Based on the bp's weight in grams taken into account, 15 -20% of that weight is a good estimate of what the prey item should weigh. The other way is to measure the largest part of the mid body circumference and offer prey that is close to or slightly larger than that. 15%of 1000 is 150. Prey item should be 150 grams. 20% of1000 would be 200grams. There is leeway around these figures. Good luck

That 15% to 20% rule is mostly for hatchlings.

I personally don't feed a 1000g snake anything bigger than a 60g to 65g rat (or that ballpark).