Again this is down to personal preference, the best are Protektor. The front ‘Owl Ear’ bag should be to match what ever rifle you use, they come in three different width, overall they are all 51/4” but the gap between the ‘Owl Ears’ varies from 11/2” to 3” which is the maximum width allowed under the rules for a flat rifle forend. The rear bags suggested by all the top shooters are the ‘Bunny Ear ’Protektor sand bags not ‘Rabbit Ear’ these are to big. You will need at least a medium sized bag so you get the height. These bags come with either leather or Cordura ears. The Cordura are more ‘slippy’ but will lose that after use for while, you can buy a replenishing silicon spray from Sinclair in the US. The leather ones I find are best and if necessary talcum powder or a spray deodorant can be applied to make more ‘slippy’. I have never found this necessary.