Check the listing for details. Walex Porta-pak Black Holding Tank Deodorizer & Portion Control System. Color: Blue, Condition: New, Made in United States. Listed at 14.18 USD. WASTE BREAKDOWN - Porta-Pak RV Marine Holding Tank Deodorizer breaks down waste and stubborn RV toilet paper, keeping your holding tank sensors working effectively. No more clogs or backups. HOLDING TANK DEODORIZER - Porta-Pak marine and RV holding tank deodorizer tackles unpleasant smells. Say goodbye to embarrassing odors with your boat, camping toilet, and RV toilet tabs. VERSATILE FOR ALL TANKS - Our marine and RV tank deodorizer for black tank cleans tanks from 2.5 gallons - 40 gallons. Ideal for RVing, boating, boondocking, and portable camping cassette toilets. FRESH 10 PACK - Our marine and RV drop ins for toilets dissolve immediately upon contact with water. Just Drop it in - no messy spills. Non-staining color.