Thake a word of advice, buy the M300, you can by pads for it on ebay/amazon for pennies, if you tight, refill the gas canisters[you tube] Clip it to you trouser, belt pocket etc and everywhere you go no biters within 20 feet, they are so unobtrusive you wont notice them. Why buy the big bulky things if not needed. Only time I would use one of them is in a great big indoor area , log cabin or the like.