I've assembled over 1000,own 500,&the only complaint is beetles like the top slot .If put in the hive just before flow the bees fill the slot,if not melt a little wax to fill it.I've assembled over 3000 frames this spring[few 75-90 yr old beeks here&I have air tools to their hammers]&IMO the time to fill the top slot is worth it&they square up&fit well.