I have had the WBT bananas, which use the same attachment process. It’s not required, but it sure does help. However you can get the sleeves cheap at Parts Connexion and a number of < $20 electrician’s crimpers like this one will do the job just as well as the WBT tool. Try to leave as little exposed wire between the cable insulator and the sleeve to minimize the possibility of shorting after installation.
Also, be careful not to loose the wrench that comes with the plugs as the nuts are easy to strip with the wrong tool.