I made mine 14 years ago and they are virtually indestructible. Every year I clean them in hot soapy water, rewrite the numbers in black sharpie, and they're good to go. My students keep them in their desks and use them whenever they like.
If you're interested, here are the directions for making them. This is what you'll need:
- 3/4" PVC tubing
- 3/4" PVC elbows
You can find the tubing and elbows at Home Depot or Lowe's. I was totally clueless about PVC tubing! Just ask someone there. You'll need two elbows for each phone. Cut the tubing into 3 1/2" lengths, then attach an elbow to each end.
Using a permanent marker, put a number on each phone. Each student keeps their phone in their desk, to use as needed.
If you want a larger diameter phone, just use a larger pipe (1" or larger). The 3 1/2" tube length seems to be about the right size for primary students.
If you feel like spending money on the commercially made phones, you can find them sold as whisperphones, toobaloos, and phonics phones.
Right track reading has a very detailed article about reading phones and why research supports their usage with students.
If you haven't made a set, try it! They are so easy to make and your students will LOVE them!