I put the students into pairs/groups and give each one the required materials. Their objective is to go outside and find as many things as they can that are EXACTLY
1 inch (you can use different measurements each time). Then they place the item in the baggie and write down what it is. It is easy to count how many things they found if they write it down and the group with the most items gets an award. If there is time I also have them put all the items on their desk and the group next to them has to go through and make sure each item is EXACT. Be sure to cover your behavioral expectations before they go outside. I also did this inside on a rainy day and they loved it.