Isn't the Athlon 3-15x50 FFP an ETR and not a BTR.....I could well be wrong! If it is, it has a 34mm tube but is a fantastic scopemat at that price, usually about a grand! I have the BTR Gen2 2.5-15x50 FFP...awesome scope with a 30mm tube, the G3 will be even better like Steve said above.